CALIBRE-SMTP(1)

✨ NAME ✨

calibre-smtp — okay so bestie, this is the calibre manual's very own calibre-smtp(1) situation, and it is literally the tool that sends mail using the SMTP protocol 💌

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🌸 SYNOPSIS 🌸

calibre-smtp [options] [from to text]

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🦋 DESCRIPTION 🦋

Send mail using the SMTP protocol. No cap, that's the whole gig. calibre-smtp has two modes of operation, and honestly she's flexible like that:

• In the compose mode you specify from to and text, and these are used to build and send an email message ✨
• In the filter mode, calibre-smtp reads a complete email message from STDIN and sends it 💅

text is the body of the email message. If text is not specified, a complete email message is read from STDIN.

from is the email address of the sender and to is the email address of the recipient. And here's the lil plot twist 👀 when a complete email is read from STDIN, from and to are only used in the SMTP negotiation — the message headers are not modified.

⚠️ Whenever you pass arguments to calibre-smtp that have spaces in them, enclose the arguments in quotation marks. For example: "/some path/with spaces" — the spaces will absolutely betray you otherwise 🫶

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💖 OPTIONS 💖

• --fork, -f — Fork and deliver message in background. If you use this option, you should also use --outbox to handle delivery failures. (main character energy, but make sure someone catches her if she trips 🎀)
• --help, -h — show this help message and exit
• --localhost, -l — Host name of localhost. Used when connecting to SMTP server.
• --outbox, -o — Path to maildir folder to store failed email messages in.
• --timeout, -t — Timeout for connection
• --verbose, -v — Be more verbose
• --version — show program's version number and exit

📬 COMPOSE MAIL 📬

Options to compose an email. Ignored if text is not specified — like, she's not gonna build a message out of thin air bestie 😭

• --attachment, -a — File to attach to the email
• --subject, -s — Subject of the email

🌈 SMTP RELAY 🌈

Options to use an SMTP relay server to send mail. calibre will try to send the email directly unless --relay is specified. So the relay is opt-in, periodt 💅

• --cafile — Path to a file of concatenated CA certificates in PEM format, used to verify the server certificate when using TLS. By default, the system CA certificates are used.
• --dont-verify-server-certificate — Do not verify the server certificate when connecting using TLS. This used to be the default behavior in calibre versions before 3.27. If you are using a relay with a self-signed or otherwise invalid certificate, you can use this option to restore the pre 3.27 behavior.
• --encryption-method, -e — Encryption method to use when connecting to relay. Choices are TLS, SSL and NONE. Default is TLS. > ⚠️ WARNING: Choosing NONE is highly insecure. Like, do not unless you truly know what you're doing 🙈
• --password, -p — Password for relay
• --port — Port to connect to on relay server. Default is to use 465 if encryption method is SSL and 25 otherwise.
• --relay, -r — An SMTP relay server to use to send mail.
• --username, -u — Username for relay

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👑 AUTHOR 👑

Kovid Goyal

🎀 COPYRIGHT 🎀

Kovid Goyal

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okay that's the whole page, you ate that 💖 This was calibre-smtp from the calibre manual, version 9.14.0, dated August 28, 2026 — mwah, go send some mail bestie, ily 🫶✨💅