imapsync - Email IMAP tool for syncing, copying, migrating and archiving email mailboxes between two imap servers, one way, and without du...



imapsync − Email IMAP tool for syncing, copying, migrating and archiving email mailboxes between two imap servers, one way, and without duplicates.


This documentation refers to Imapsync $Revision: 2.229 $


To synchronize the source imap account
"test1" on server "" with password "secret1"
to the destination imap account
"test2" on server "" with password "secret2"
imapsync \
−−host1 −−user1 test1 −−password1 secret1 \
−−host2 −−user2 test2 −−password2 secret2


We sometimes need to transfer mailboxes from one imap server to one another.

Imapsync command is a tool allowing incremental and recursive imap transfers from one mailbox to another. If you don’t understand the previous sentence, it’s normal, it’s pedantic computer-oriented jargon.

All folders are transferred, recursively, meaning the whole folder hierarchy is taken, all messages in them, and all message flags (\Seen \Answered \Flagged etc.) are synced too.

Imapsync reduces the amount of data transferred by not transferring a given message if it already resides on the destination side. Messages that are on the destination side but not on the source side stay as they are. See the −−delete2 option to have strict sync and delete them.

How does imapsync know a message is already on both sides? Same specific headers and the transfer is done only once. By default, the identification headers are "Message-Id:" and "Received:" lines but this choice can be changed with the −−useheader option, most often a duplicate problem is solved by using −−useheader "Message-Id"

All flags are preserved, unread messages will stay unread, read ones will stay read, deleted will stay deleted. In the IMAP protocol, a deleted message is not deleted, it is marked \Deleted and can be undeleted. Real destruction comes with the EXPUNGE or UIDEXPUNGE IMAP commands.

You can abort the transfer at any time and restart it later, imapsync works well with bad connections and interruptions, by design. On a terminal hit Ctr-c twice within two seconds to abort the program. Hit Ctr-c just once makes imapsync reconnect to both imap servers.

How do you know the sync is finished and well done? When imapsync ends by itself it mentions it with lines like those:

Exiting with return value 0 (EX_OK: successful termination) 0/50 nb_errors/max_errors PID 301
Removing pidfile /tmp/
Log file is LOG_imapsync/2020_11_17_15_59_22_761_test1_test2.txt ( to change it, use −−logfile filepath ; or use −−nolog to turn off logging )

If you don’t have those lines it means that either the sync process is still running (or eventually hanging indefinitely) or that it ended without a whisper, a strong kill −9 on Linux for example.

If you have those final lines then it means the sync process is properly finished. It may have encountered problems though.

A good synchronization is mentioned by some lines above the last ones, especially those three lines:

The sync looks good, all 1745 identified messages in host1 are on host2.
There is no unidentified message on host1.
Detected 0 errors

Imapsync mentions the total sizes of both accounts at the beginning of the sync and also at the end. Sometimes, even with a strict sync, those total sizes differ, and sometimes they differ a lot. The difference is not a good criterion to conclude the sync went wrong.

Why? That’s because message sizes given by the imap servers are not always accurate, they are not always the same as the actual message sizes of the messages transferred by imapsync. Imapsync use the sizes given by the imap servers to calculate the big total size. They can differ. In the early days, Imapsync used the sizes of the messages as one of the criteria to identify the messages, different sizes implied different messages; but it was a mistake, the same message had different sizes on both sides sometimes, depending on the imap servers.

Another explanation for a big total size difference is that Gmail doesn’t count the size of duplicate messages across folders twice, while imapsync does.

A classical scenario is synchronizing a mailbox B from another mailbox A where you just want to keep a strict copy of A in B. Strict meaning all messages in A will be in B but no more.

For a strict synchronization, use the option −−delete2. The option −−delete2 deletes the messages in the host2 folder B that are not in the host1 folder A. If you also need to destroy host2 folders that are not in host1 then use −−delete2folders. See also −−delete2foldersonly and −−delete2foldersbutnot to set up exceptions on folders to destroy. INBOX will never be destroyed, it’s a mandatory folder in IMAP so imapsync doesn’t even try to remove it.

A different scenario is to delete the messages from the source mailbox after a successful transfer, it can be a good feature when migrating mailboxes since messages will be only on one side. The source account will only have messages that are not on the destination yet, ie, messages that arrived after a sync or that failed to be transferred.

In that case, use the −−delete1 option. Option −−delete1 implies also the option −−expunge1 so all messages marked deleted on host1 will be deleted. In IMAP protocol deleting a message does not delete it, it marks it with the flag \Deleted, allowing an undelete. Expunging a folder removes, definitively, all the messages marked as \Deleted in this folder.

You can also decide to remove empty folders once all of their messages have been transferred. Add −−delete1emptyfolders to obtain this behavior.

Imapsync is not adequate for maintaining two active imap accounts in synchronization when the user plays independently on both sides. Use offlineimap (written by John Goerzen) or mbsync (written by Michael R. Elkins) for a 2 ways synchronization.


usage: imapsync [options]

The standard options are the six values forming the credentials. Three values on each side are needed to login into the IMAP servers. These six values are a hostname, a username, and a password, two times.

Here are the conventions used in the following descriptions of the options:

str means a string
int means an integer number
flo means a float number
reg means a regular expression
cmd means a command
−−dry : Makes imapsync do nothing for real; it just prints what
would be done without −−dry.


−−host1 str : Source or "from" imap server.
−−port1 int : Port to connect on host1.
Optional since default ports are the
well known ports imap/143 or imaps/993.
−−user1 str : User to login on host1.
−−password1 str : Password of user1.
−−host2 str : "destination" imap server.
−−port2 int : Port to connect on host2. Optional
−−user2 str : User to login on host2.
−−password2 str : Password of user2.
−−showpasswords : Shows passwords on output instead of "MASKED".
Useful to restart a complete run by just reading
the command line used in the log,
or to debug passwords.
It's not a secure practice at all!
−−passfile1 str : Password file for the user1. It must contain the
password on the first line. This option avoids showing
the password on the command line like −−password1 does.
−−passfile2 str : Password file for the user2.

You can also pass the passwords in the environment variables IMAPSYNC_PASSWORD1 and IMAPSYNC_PASSWORD2. If you don’t pass the user1 password via −−password1 nor −−passfile1 nor $IMAPSYNC_PASSWORD1 then imapsync will prompt to enter the password on the terminal. Same thing for user2 password.


−−nossl1 : Do not use a SSL connection on host1.
−−ssl1 : Use a SSL connection on host1. On by default if possible.
−−nossl2 : Do not use a SSL connection on host2.
−−ssl2 : Use a SSL connection on host2. On by default if possible.
−−notls1 : Do not use a TLS connection on host1.
−−tls1 : Use a TLS connection on host1. On by default if possible.
−−notls2 : Do not use a TLS connection on host2.
−−tls2 : Use a TLS connection on host2. On by default if possible.
−−debugssl int : SSL debug mode from 0 to 4.
−−sslargs1 str : Pass any ssl parameter for host1 ssl or tls connection. Example:
−−sslargs1 SSL_verify_mode=1 −−sslargs1 SSL_version=SSLv3
See all possibilities in the new() method of IO::Socket::SSL
−−sslargs2 str : Pass any ssl parameter for host2 ssl or tls connection.
See −−sslargs1


−−authmech1 str : Auth mechanism to use with host1:
−−authmech2 str : Auth mechanism to use with host2. See −−authmech1
−−authuser1 str : User to auth with on host1 (admin user).
Avoid using −−authmech1 SOMETHING with −−authuser1.
−−authuser2 str : User to auth with on host2 (admin user).
−−proxyauth1 : Use proxyauth on host1. Requires −−authuser1.
Required by Sun/iPlanet/Netscape IMAP servers to
be able to use an administrative user.
−−proxyauth2 : Use proxyauth on host2. Requires −−authuser2.
−−authmd51 : Use MD5 authentication for host1.
−−authmd52 : Use MD5 authentication for host2.
−−domain1 str : Domain on host1 (NTLM authentication).
−−domain2 str : Domain on host2 (NTLM authentication).
−−oauthaccesstoken1 str : The access token to authenticate with OAUTH2.
It will be combined with the −−user1 value to form the
string to pass with XOAUTH2 authentication.
The password given by −−password1 or −−passfile1
is ignored but needed on the command line.
Instead of the access token itself, the value can be a
file containing the access token on the first line.
If the value is a file, imapsync reads its first line
and take this line as the access token. The advantage
of the file is that if the access token changes then
imapsync can read it again when it needs to reconnect
during a run.
−−oauthaccesstoken2 str : same thing as −−oauthaccesstoken1
−−oauthdirect1 str : The direct string to pass with XOAUTH2 authentication.
The password given by −−password1 or −−passfile1 and
the user given by −−user1 are ignored but they are
needed to be on the command line. Consider it a bug.
−−oauthdirect2 str : same thing as oauthdirect1


−−folder str : Sync this folder.
−−folder str : and this one, etc.
−−folderrec str : Sync this folder recursively.
−−folderrec str : and this one, etc.
−−folderfirst str : Sync this folder first. Ex. −−folderfirst "INBOX"
−−folderfirst str : then this one, etc.
−−folderlast str : Sync this folder last. −−folderlast "[Gmail]/All Mail"
−−folderlast str : then this one, etc.
−−nomixfolders : Do not merge folders when host1 is case−sensitive
while host2 is not (like Exchange). Only the first
similar folder is synced. Example: with folders
"Sent", "SENT" and "sent" on host1, only "Sent"
will be synced to host2.
−−skipemptyfolders : Empty host1 folders are not created on host2.
−−include reg : Sync folders matching this regular expression
−−include reg : or this one, etc.
If both −−include −−exclude options are used, then
include is done before.
−−exclude reg : Skips folders matching this regular expression
Several folders to avoid:
−−exclude 'fold1|fold2|f3' skips fold1, fold2 and f3.
−−exclude reg : or this one, etc.
−−automap : guesses folders mapping, for folders well known as
"Sent", "Junk", "Drafts", "All", "Archive", "Flagged".
−−f1f2 str1=str2 : Force folder str1 to be synced to str2,
−−f1f2 overrides −−automap and −−regextrans2.
Use several −−f1f2 options to map several folders.
Option −−f1f2 is a one to one only folder mapping,
str1 and str2 have to be full path folder names.
−−subfolder2 str : Syncs the whole host1 folders hierarchy under the
host2 folder named str.
It does it internally by adding three
−−regextrans2 options before all others.
Add −−debug to see what's really going on.
−−subfolder1 str : Syncs the host1 folders hierarchy which is under folder
str to the root hierarchy of host2.
It's the couterpart of a sync done by −−subfolder2
when doing it in the reverse order.
Backup/Restore scenario:
Use −−subfolder2 str for a backup to the folder str
on host2. Then use −−subfolder1 str for restoring
from the folder str, after inverting
host1/host2 user1/user2 values.
−−subscribed : Transfers subscribed folders.
−−subscribe : Subscribe to the folders transferred on the
host2 that are subscribed on host1. On by default.
−−subscribeall : Subscribe to the folders transferred on the
host2 even if they are not subscribed on host1.
−−prefix1 str : Remove prefix str to all destination folders,
usually "INBOX." or "INBOX/" or an empty string "".
imapsync guesses the prefix if host1 imap server
does not have NAMESPACE capability. So this option
should not be used most of the time.
−−prefix2 str : Add prefix to all host2 folders. See −−prefix1
−−sep1 str : Host1 separator. This option should not be used
most of the time.
Imapsync gets the separator from the server itself,
by using NAMESPACE, or it tries to guess it
from the folders listing (it counts
characters / . \\ \ in folder names and choose the
more frequent, or finally / if nothing is found.
−−sep2 str : Host2 separator. See −−sep1
−−regextrans2 reg : Apply the whole regex to each destination folders.
−−regextrans2 reg : and this one. etc.
When you play with the −−regextrans2 option, first
add also the safe options −−dry −−justfolders
Then, when happy, remove −−dry for a run, then
remove −−justfolders for the next ones.
Have in mind that −−regextrans2 is applied after
the automatic prefix and separator inversion.
For examples see:

OPTIONS/folders sizes

−−nofoldersizes : Do not calculate the size of each folder at the
beginning of the sync. Default is to calculate them.
−−nofoldersizesatend: Do not calculate the size of each folder at the
end of the sync. Default is to calculate them.
−−justfoldersizes : Exit after having printed the initial folder sizes.


−−tmpdir str : Where to store temporary files and subdirectories.
Will be created if it doesn't exist.
Default is system specific, Unix is /tmp but
/tmp is often too small and deleted at reboot.
−−tmpdir /var/tmp should be better.
−−pidfile str : The file where imapsync pid is written,
it can be dirname/filename complete path.
The default name is in tmpdir.
−−pidfilelocking : Abort if pidfile already exists. Useful to avoid
concurrent transfers on the same mailbox.


−−nolog : Turn off logging on file
−−logfile str : Change the default log filename (can be dirname/filename).
−−logdir str : Change the default log directory. Default is LOG_imapsync/

The default logfile name is for example



2019_12_22_23_57_59_532 is nearly the date of the start

and user1 user2 are the −−user1 −−user2 values.


−−skipmess reg : Skips messages matching the regex.
Example: 'm/[\x80−\xff]/' # to avoid 8bits messages.
−−skipmess is applied before −−regexmess
−−skipmess reg : or this one, etc.
−−skipcrossduplicates : Avoid copying messages that are already copied
in another folder, good from Gmail to XYZ when
XYZ is not also Gmail.
Activated with −−gmail1 unless −−noskipcrossduplicates
−−debugcrossduplicates : Prints which messages (UIDs) are skipped with
−−skipcrossduplicates and in what other folders
they are.
−−pipemess cmd : Apply this cmd command to each message content
before the copy.
−−pipemess cmd : and this one, etc.
With several −−pipemess, the output of each cmd
command (STDOUT) is given to the input (STDIN)
of the next command.
For example,
−−pipemess cmd1 −−pipemess cmd2 −−pipemess cmd3
is like a Unix pipe:
"cat message | cmd1 | cmd2 | cmd3"
−−disarmreadreceipts : Disarms read receipts (host2 Exchange issue)
−−regexmess reg : Apply the whole regex to each message before transfer.
Example: 's/\000/ /g' # to replace null characters
by spaces.
−−regexmess reg : and this one, etc.
−−truncmess int : truncates messages when their size exceed the int
value, specified in bytes. Good to sync too big
messages or to "suppress" attachments.
Have in mind that this way, messages become
uncoherent somehow.


Gmail present labels as folders in imap. Imapsync can accelerate the sync by syncing X−GM-LABELS, it will avoid to transfer messages when they are already on host2 in another folder.

−−synclabels : Syncs also Gmail labels when a message is copied to host2.
Activated by default with −−gmail1 −−gmail2 unless
−−nosynclabels is added.
−−resynclabels : Resyncs Gmail labels when a message is already on host2.
Activated by default with −−gmail1 −−gmail2 unless
−−noresynclabels is added.

For Gmail syncs, see also:


If you encounter flag problems see also:
−−regexflag reg : Apply the whole regex to each flags list.
Example: 's/"Junk"//g' # to remove "Junk" flag.
−−regexflag reg : then this one, etc.
−−resyncflags : Resync flags for already transferred messages.
On by default.
−−noresyncflags : Do not resync flags for already transferred messages.
May be useful when a user has already started to play
with its host2 account.
−−filterbuggyflags : Filter flags known to be buggy and generators of errors
"BAD Invalid system flag" or "NO APPEND Invalid flag list".


−−delete1 : Deletes messages on host1 server after a successful
transfer. Option −−delete1 has the following behavior:
it marks messages as deleted with the IMAP flag
\Deleted, then messages are really deleted with an
EXPUNGE IMAP command. If expunging after each message
slows down too much the sync then use
−−noexpungeaftereach to speed up, expunging will then be
done only twice per folder, one at the beginning and
one at the end of a folder sync.
−−expunge1 : Expunge messages on host1 just before syncing a folder.
Expunge is done per folder.
Expunge aims is to really delete messages marked deleted.
An expunge is also done after each message copied
if option −−delete1 is set (unless −−noexpungeaftereach).
−−noexpunge1 : Do not expunge messages on host1.
−−delete1emptyfolders : Deletes empty folders on host1, INBOX excepted.
Useful with −−delete1 since what remains on host1
is only what failed to be synced.
−−delete2 : Delete messages in the host2 account that are not in
the host1 account. Useful for backup or pre−sync.
−−delete2 implies −−uidexpunge2
−−delete2duplicates : Deletes messages in host2 that are duplicates in host2.
Works only without −−useuid since duplicates are
detected with an header part of each message.
NB: −−delete2duplicates is far less violent than −−delete2
since it removes only duplicates.
−−delete2folders : Delete folders in host2 that are not in host1.
For safety, first try it like this, it is safe:
−−delete2folders −−dry −−justfolders −−nofoldersizes
and see what folders will be deleted.
−−delete2foldersonly reg : Delete only folders matching the regex reg.
Example: −−delete2foldersonly "/ˆJunk$|ˆINBOX.Junk$/"
This option activates −−delete2folders
−−delete2foldersbutnot reg : Do not delete folders matching the regex rex.
Example: −−delete2foldersbutnot "/Tasks$|Contacts$|Foo$/"
This option activates −−delete2folders
−−noexpunge2 : Do not expunge messages on host2.
−−nouidexpunge2 : Do not uidexpunge messages on the host2 account
that are not on the host1 account.


If you encounter problems with dates, see also:
−−syncinternaldates : Sets the internal dates on host2 as the same as host1.
Turned on by default. Internal date is the date
a message arrived on a host (Unix mtime usually).
−−idatefromheader : Sets the internal dates on host2 as same as the
ones in "Date:" headers.

OPTIONS/message selection

−−maxsize int : Skip messages larger (or equal) than int bytes
−−minsize int : Skip messages smaller (or equal) than int bytes
−−maxage int : Skip messages older than int days.
final stats (skipped) don't count older messages
see also −−minage
−−minage int : Skip messages newer than int days.
final stats (skipped) don't count newer messages
You can do (+ zone are the messages selected):
past|−−−−maxage+++++minage−−−−>now (intersection)
past|++++minage−−−−−maxage++++>now (union)
−−search str : Selects only messages returned by this IMAP SEARCH
command. Applied on both sides.
For a complete set of what can be search see
−−search1 str : Same as −−search but for selecting host1 messages only.
−−search2 str : Same as −−search but for selecting host2 messages only.
So −−search CRIT equals −−search1 CRIT −−search2 CRIT
−−noabletosearch : Makes −−minage and −−maxage options use the internal
dates given by a FETCH imap command instead of the
"Date:" header. Internal date is the arrival date
in the mailbox.
−−noabletosearch equals −−noabletosearch1 −−noabletosearch2
−−noabletosearch1 : Like −−noabletosearch but for host1 only.
−−noabletosearch2 : Like −−noabletosearch but for host2 only.
−−maxlinelength int : skip messages with a line length longer than int bytes.
RFC 2822 says it must be no more than 1000 bytes but
real life servers and email clients do more.
−−useheader str : Use this header to compare messages on both sides.
Example: "Message−Id" or "Received" or "Date".
−−useheader str and this one, etc.
−−syncduplicates : Sync also duplicates. Off by default.
−−usecache : Use cache to speed up next syncs. Off by default.
−−nousecache : Do not use cache. Caveat: −−useuid −−nousecache creates
duplicates on multiple runs.
−−useuid : Use UIDs instead of headers as a criterion to recognize
messages. Option −−usecache is then implied unless
−−nousecache is used.


−−syncacls : Synchronizes acls (Access Control Lists).
Acls in IMAP are not standardized, be careful
since one acl code on one side may signify something
else on the other one.
−−nosyncacls : Does not synchronize acls. This is the default.
−−addheader : When a message has no headers to be identified,
−−addheader adds a "Message−Id" header,
like "Message−Id: 12345@imapsync", where 12345
is the imap UID of the message on the host1 folder.
Useful to sync folders "Sent" or "Draft".


−−debug : Debug mode.
−−debugfolders : Debug mode for the folders part only.
−−debugcontent : Debug content of the messages transferred. Huge output.
−−debugflags : Debug mode for flags.
−−debugimap1 : IMAP debug mode for host1. Very verbose.
−−debugimap2 : IMAP debug mode for host2. Very verbose.
−−debugimap : IMAP debug mode for host1 and host2. Twice very verbose.
−−debugmemory : Debug mode showing memory consumption after each copy.
−−errorsmax int : Exit when int number of errors is reached. Default is 50.
−−tests : Run local non−regression tests. Exit code 0 means all ok.
−−testslive : Run a live test with imap server.
Useful to check the basics. Needs internet connection.
−−testslive6 : Run a live test with imap server.
Useful to check the ipv6 connectivity. Needs internet.


−−gmail1 : sets −−host1 to Gmail and other options. See FAQ.Gmail.txt
−−gmail2 : sets −−host2 to Gmail and other options. See FAQ.Gmail.txt
−−office1 : sets −−host1 to Office365 and other options. See FAQ.Office365.txt
−−office2 : sets −−host2 to Office365 and other options. See FAQ.Office365.txt
−−exchange1 : sets options for Exchange. See FAQ.Exchange.txt
−−exchange2 : sets options for Exchange. See FAQ.Exchange.txt
−−domino1 : sets options for Domino. See FAQ.Domino.txt
−−domino2 : sets options for Domino. See FAQ.Domino.txt


−−timeout1 flo : Connection timeout in seconds for host1.
Default is 120 and 0 means no timeout at all.
−−timeout2 flo : Connection timeout in seconds for host2.
Default is 120 and 0 means no timeout at all.
Caveat, under CGI context, you may encounter a timeout
from the webserver, killing imapsync and the imap connections.
See the document INSTALL.OnlineUI.txt and search
for "Timeout" for how to deal with this issue.
−−keepalive1 :
Some firewalls and network gears like to timeout connections
prematurely if the connection sits idle.
This option enables SO_KEEPALIVE on the host1 socket.
−−keepalive1 is on by default since imapsync release 2.169
Use −−nokeepalive1 to disable it.
−−keepalive2 : Same as −−keepalive2 but for host2.
Use −−nokeepalive2 to disable it.
−−maxmessagespersecond flo : limits the average number of messages
transferred per second.
−−maxbytespersecond int : limits the average transfer rate per second.
−−maxbytesafter int : starts −−maxbytespersecond limitation only after
−−maxbytesafter amount of data transferred.
−−maxsleep flo : do not sleep more than int seconds.
On by default, 2 seconds max, like −−maxsleep 2
−−abort : terminates a previous call still running.
It uses the pidfile to know what process to abort.
−−exitwhenover int : Stop syncing and exits when int total bytes
transferred is reached.
−−version : Print only the software version.
−−noreleasecheck : Do not check for any new imapsync release.
−−releasecheck : Check for new imapsync release.
it's an http request to
−−emailreport1 : Put the email final report in host1 INBOX
−−emailreport2 : Put the email final report in host2 INBOX
−−noemailreport1 : Do not put the email final report in host1 INBOX
−−noemailreport2 : Do not put the email final report in host2 INBOX
−−noid : Do not send/receive IMAP "ID" command to imap servers.
−−justconnect : Just connect to both servers and print useful
information. Need only −−host1 and −−host2 options.
Obsolete since "imapsync −−host1 imaphost" alone
implies −−justconnect
−−justlogin : Just login to both host1 and host2 with users
credentials, then exit.
−−justfolders : Do only things about folders (ignore messages).
−−help : print this help.
Example: to synchronize imap account "test1" on ""
to imap account "test2" on ""
with test1 password "secret1"
and test2 password "secret2"
imapsync \
−−host1 −−user1 test1 −−password1 secret1 \
−−host2 −−user2 test2 −−password2 secret2


You can use −−passfile1 instead of −−password1 to mention the password since it is safer. With −−password1 option, on Linux, any user on your host can see the password by using the ’ps auxwwww’ command. Using a variable (like IMAPSYNC_PASSWORD1) is also dangerous because of the ’ps auxwwwwe’ command. So, saving the password in a well protected file (600 or rw−−−−−−−) is the best solution.

Imapsync activates ssl or tls encryption by default, if possible.

What detailed behavior is under this "if possible"?

Imapsync activates ssl if the well known port imaps port (993) is open on the imap servers. If the imaps port is closed then it open a normal (clear) connection on port 143 but it looks for TLS support in the CAPABILITY list of the servers. If TLS is supported then imapsync goes to encryption with STARTTLS.

If the automatic ssl and the tls detections fail then imapsync will not protect against sniffing activities on the network, especially for passwords.

If you want to force ssl or tls just use −−ssl1 −−ssl2 or −−tls1 −−tls2

See also the document FAQ.Security.txt in the FAQ.d/ directory or at


Imapsync will exit with a 0 status (return code) if everything went good. Otherwise, it exits with a non-zero status. That’s classical Unix behavior. Here is the list of the exit code values (an integer between 0 and 255). In Bourne Shells, this exit code value can be retrieved within the variable value "$?" if you read it just after the imapsync call.

The names reflect their meaning:

EX_OK => 0 ; #/* successful termination */
EX_USAGE => 64 ; #/* command line usage error */
EX_NOINPUT => 66 ; #/* cannot open input */
EX_UNAVAILABLE => 69 ; #/* service unavailable */
EX_SOFTWARE => 70 ; #/* internal software error */
EXIT_CATCH_ALL => 1 ; # Any other error
EXIT_BY_SIGNAL => 6 ; # Should be 128+n where n is the sig_num
EXIT_TESTS_FAILED => 254 ; # Like Test::More API


Imapsync is free, open, public but not always gratis software cover by the NOLIMIT Public License, now called NLPL. See the LICENSE file included in the distribution or just read the following simple sentence as it IS the license text:

"No limits to do anything with this work and this license."

In case it is not long enough, I repeat:

"No limits to do anything with this work and this license."

Look at


Gilles LAMIRAL <[email protected]>

Good feedback is always welcome. Bad feedback is very often welcome.

Gilles LAMIRAL earns his living by writing, installing, configuring and sometimes teaching free, open, and often gratis software. Imapsync used to be "always gratis" but now it is only "often gratis" because imapsync is sold by its author, your servitor, a good way to maintain and support free open public software tools over decades.



IMAP SERVERS supported



If you have many mailboxes to migrate think about a little shell program. Write a file called file.txt (for example) containing users and passwords. The separator used in this example is ’;’

The file.txt file contains:

user001_1;password001_1;user001_2;password001_2 user002_1;password002_1;user002_2;password002_2 user003_1;password003_1;user003_2;password003_2 user004_1;password004_1;user004_2;password004_2 user005_1;password005_1;user005_2;password005_2 ...

On Unix the shell program can be:

{ while IFS=';' read u1 p1 u2 p2; do
imapsync −−host1 −−user1 "$u1" −−password1 "$p1" \
−−host2 −−user2 "$u2" −−password2 "$p2" ...
done ; } < file.txt

On Windows the batch program can be:

FOR /F "tokens=1,2,3,4 delims=; eol=#" %%G IN (file.txt) DO imapsync ˆ
−−host1 −−user1 %%G −−password1 %%H ˆ
−−host2 −−user2 %%I −−password2 %%J ...

The ... have to be replaced by nothing or any imapsync option. Welcome in shell or batch programming !

You will find already written scripts at


Imapsync works under any Unix with Perl.
Imapsync works under most Windows (2000, XP, Vista, Seven, Eight, Ten
and all Server releases 2000, 2003, 2008 and R2, 2012 and R2, 2016)
as a standalone binary software called imapsync.exe, usually launched
from a batch file in order to avoid always typing the options. There
is also a 32bit binary called imapsync_32bit.exe
Imapsync works under OS X as a standalone binary software called
Purchase latest imapsync at
You'll receive a link to a compressed tarball called
imapsync−x.xx.tgz where x.xx is the version number.
Untar the tarball where you want (on Unix):
tar xzvf imapsync−x.xx.tgz
Go into the directory imapsync−x.xx and read the INSTALL file.
As mentioned at
the INSTALL file can also be found at
It is now split in several files for each system


There is no specific configuration file for imapsync, everything is specified by the command line parameters and the default behavior.


Feel free to hack imapsync as the NOLIMIT license permits it.


See also
for a better up to date list.

List verified on Friday July 1, 2021.

imapsync: (this is an imapsync copy, sometimes delayed, with −−noreleasecheck by default since release 1.592, 2014/05/22)
imap_tools: The imap_tools code is now at−sanders−imap−tools
imaputils: (very old imap_tools fork)
Doveadm−Sync: ( Dovecot sync tool )
mailutil: part of the UW IMAP toolkit. (well, seems abandoned now)
imapcopy (Pascal):
imapcopy (Java):
larch: (derived from wonko_imapsync, good at Gmail)
wonko_imapsync: (superseded by larch)
pop2imap: http://www.linux− (I wrote that too)
exchange−away: http://exchange−
imap−upload: http://imap− (A tool for uploading a local mbox file to IMAP4 server)
imapbackup: (A Python script for incremental backups of IMAP mailboxes)
BitRecover email−backup 99 USD, 299 USD−backup/.
ImportExportTools:−us/thunderbird/addon/importexporttools/ ImportExportTools for Mozilla Thunderbird by Paolo Kaosmos. ImportExportTools does not do IMAP.
CodeTwo: but CodeTwo does imap source to Office365 only.


I initially wrote imapsync in July 2001 because an enterprise, called BaSystemes, paid me to install a new imap server without losing huge old mailboxes located in a far away remote imap server, accessible by an often broken low-bandwidth ISDN link.

I had to verify every mailbox was well transferred, all folders, all messages, without wasting bandwidth or creating duplicates upon resyncs. The imapsync design was made with the beautiful rsync command in mind.

Imapsync started its life as a patch of the script. The script comes from the Mail−IMAPClient−2.1.3 perl module tarball source (more precisely in the examples/ directory of the Mail-IMAPClient tarball).

So many changes happened since then that I wonder if it remains any lines of the original in imapsync source code.

Updated 2024-01-29 - |