SMTP(1) General Commands Manual SMTP(1)
NAME
smtp — Simple Mail Transfer Protocol client
SYNOPSIS
smtp [−Chnv] [−a authfile] [−F from] [−H helo] [−s server] [−T params] [recipient ...]
DESCRIPTION
The smtp utility is a Simple Mail Transfer Protocol (SMTP) client which can be used to run an SMTP transaction against an SMTP server.
By default, smtp reads the mail content from the standard input, establishes an SMTP session, and runs an SMTP transaction for all the specified recipients. The content is sent unaltered as mail data.
The options are as follows:
−a authfile
Perform a login before sending the message. The username and password are read from authfile and need to be on the first and second line respectively. This option requires a TLS or STARTTLS server.
−C
Do not require server certificate to be valid. This flag is deprecated. Use “−T noverify” instead.
−F from
Set the return-path (MAIL FROM) for the SMTP transaction. Default to the current username.
−H helo
Define the hostname to advertise (HELO) when establishing the SMTP session.
−h
Display usage.
−n
Do not actually execute a transaction, just try to establish an SMTP session and quit. When this option is given, no message is read from the standard input.
−s server
Specify the server to connect to and connection parameters. The format is [proto://[user:pass@]]host[:port]. The following protocols are available:
smtp
Normal SMTP session with opportunistic STARTTLS.
smtp+tls
Normal SMTP session with mandatory STARTTLS.
smtp+notls
Plain text SMTP session without TLS.
lmtp
LMTP session with opportunistic STARTTLS.
lmtp+tls
LMTP session with mandatory STARTTLS.
lmtp+notls
Plain text LMTP session without TLS.
smtps
SMTP session with forced TLS on connection.
Defaults to “smtp://localhost:25”.
−T params
Set specific parameters for TLS sessions. The params string is a comma or space separated list of options. The available options are:
cafile=filename
Use filename as root certificates file instead of the system default.
ciphers=value
Specify the allowed ciphers. Refer to tls_config_set_ciphers(3) for value.
nosni
Disable Server Name Indication (SNI).
noverify
Do not require server certificate to be valid.
protocols=value
Specify the protocols to use. Refer to tls_config_parse_protocols(3) for value.
servername=value
Use value for Server Name Indication (SNI). Defaults to the specified server hostname.
−v
Be more verbose. This option can be specified multiple times.
SEE ALSO
smtpd(8)
HISTORY
The smtp program first appeared in OpenBSD 6.4. GNU May 23, 2021 SMTP(1)