SMTP(1)

okay bestie, pull up a chair and grab your emotional support iced coffee ☕ because we're reading a manual page together and it's genuinely gonna be fine. this one is smtp, and it lives in the General Commands Manual (section 1, the user-facing girlies 💅). no cap, it's shorter than it looks.

✨ NAME ✨

smtp — Simple Mail Transfer Protocol client. that's her. that's the whole vibe. she speaks SMTP and she's very good at it. 🦋

🎀 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, and you use it to run an SMTP transaction against an SMTP server. that's the whole main character arc. 👑

by default? smtp reads the mail content from standard input, establishes an SMTP session, and runs an SMTP transaction for all the recipients you specified. the content gets sent unaltered as mail data — no glow-up, no edits, no notes. it goes out exactly as you wrote it, fr fr. 💌

the options are as follows, and yes we're doing all of them:

• -a authfile — perform a login before sending the message. the username and password are read from authfile, and they need to be on the first and second line respectively (username first, password second, no skipping lines bestie). 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. okay so she still works but she's retired, like a queen stepping back from the throne 👑
• -F from — set the return-path (MAIL FROM) for the SMTP transaction. defaults to the current username. so if you don't say anything, she's just gonna use who you are. identity theft? no. default behaviour? yes. 🫶
• -H helo — define the hostname to advertise (HELO) when establishing the SMTP session. it's giving "hi, it's me" energy, but you get to pick which me. ✨
• -h — display usage. the classic "help me I forgot the flags" button. 🙈
• -n — do not actually execute a transaction, just try to establish an SMTP session and quit. and when this option is given, no message is read from the standard input — so she's not even looking at your stdin, she's just vibing at the door. a vibe check, if you will. 🚪
• -s server — specify the server to connect to and connection parameters. the format is:

[proto://[user:pass@]]host[:port]

and the following protocols are available:

• smtp — normal SMTP session with opportunistic STARTTLS.
• smtp+tls — normal SMTP session with mandatory STARTTLS. she said mandatory. 💅
• 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. no negotiations, no small talk, TLS from the jump. 🔥

defaults to smtp://localhost:25. so if you say nothing at all, she's knocking on localhost port 25 like it's her ex's door. 🏠

• -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). she's being mysterious on purpose. 🕶️
  • noverify — do not require server certificate to be valid. (this is the glow-up replacement for that deprecated -C up there, iykyk.)
  • 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. so she already has a name picked out, but you can rename her. 🎀
• -v — be more verbose. and the bestie detail here: this option can be specified multiple times. stack them. pile them up. more -v, more words. 🗣️

💜 SEE ALSO 💜

smtpd(8) — go read that one next, she's the server side of the story.

🌈 HISTORY 🌈

the smtp program first appeared in OpenBSD 6.4. a legend from day one, periodt. ⭐

okay that's the whole page, you made it, I'm so proud of you 🫶 and for the record, this gorgeous little document is dated $Mdocdate: May 23 2021 $ and it signs off as SMTP(1) — so go send an email, bestie, you're literally qualified now 💖✨🧚