BOUNCE(5)

💖 BOUNCE(5) — the Postfix bounce message template format, bestie edition 💖

okay so this is BOUNCE(5), a File Formats Manual page, and it's literally all about how you customize the little letters Postfix sends when mail goes wrong (or right). sit down, grab a strawberry drink 🍓, and let's get into it.

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✨ NAME ✨

bounce — Postfix bounce message template format 🎀

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🌸 SYNOPSIS 🌸

bounce_template_file = /etc/postfix/bounce.cf

postconf -b [template_file]

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💅 DESCRIPTION 💅

The Postfix bounce(8) server is the one that produces delivery status notification (DSN) messages — you know, the "hey bestie your mail didn't make it" notes — for undeliverable mail, delayed mail, successful delivery, or address verification requests. 💌

By default, these notifications are generated from built-in templates with message headers and message text. But sites can override the built-in information by specifying a bounce template file with the bounce_template_file configuration parameter. yes, you can ✨customize✨ the drama.

This document describes the general procedure to create a bounce template file, followed by the specific details of bounce template formats. no cap.

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🦋 GENERAL PROCEDURE 🦋

To create a customized bounce template file, create a temporary copy of the file /etc/postfix/bounce.cf.default and edit the temporary file. lowkey the easiest glow-up ever.

To preview the results of $name expansions in the template text, use the command:

postconf -b temporary_file

Errors in the template will be reported to the standard error stream and to the syslog daemon. so like, they WILL tell you, don't worry 🙈

While previewing the text, be sure to pay particular attention to the expansion of time value parameters that appear in the delayed mail notification text. (that's the part that sneaks up on you, fr fr 👀)

Once the result is satisfactory, copy the template to the Postfix configuration directory and specify in main.cf something like:

/etc/postfix/main.cf:
    bounce_template_file = /etc/postfix/bounce.cf

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🎀 TEMPLATE FILE FORMAT 🎀

The template file can specify templates for failed mail, delayed mail, successful delivery or for address verification. These templates are named failure_template, delay_template, success_template and verify_template, respectively. You can but do not have to specify all four templates in a bounce template file. pick your faves, bestie 👑

Each template starts with "template_name = <<EOF" and ends with a line that contains the word "EOF" only. You can change the word EOF, but you can't enclose it in quotes as with the shell or with Perl (template_name = <<'EOF'). Here is an example:

# The failure template is used for undeliverable mail.

failure_template = <<EOF
Charset: us-ascii
From: MAILER-DAEMON (Mail Delivery System)
Subject: Undelivered Mail Returned to Sender
Postmaster-Subject: Postmaster Copy: Undelivered Mail

This is the mail system at host $myhostname.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system
EOF

The usage and specification of bounce templates is subject to the following restrictions:

• No special meaning is given to the backslash character or to leading whitespace; these are always taken literally. what you type is what you get 💯
• Inside the << context, the "$" character is special. To produce a "$" character as output, specify "$$". yes, double it up, that's the vibe check.
• Outside the << context, lines beginning with "#" are ignored, as are empty lines, and lines consisting of whitespace only. ghosted, literally 💀

Examples of all templates can be found in the file bounce.cf.default in the Postfix configuration directory.

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🌈 TEMPLATE HEADER FORMAT 🌈

The first portion of a bounce template consists of optional template headers. Some become message headers in the delivery status notification; some control the formatting of that notification. Headers not specified in a template will be left at their default value. main character energy only where you want it ✨

The following headers are supported:

• Charset: — The MIME character set of the template message text. See the "TEMPLATE MESSAGE TEXT FORMAT" description below. 👀
• From: — The sender address in the message header of the delivery status notification.
• Subject: — The subject in the message header of the delivery status notification that is returned to the sender.
• Postmaster-Subject: — The subject that will be used in Postmaster copies of undeliverable or delayed mail notifications. These copies are sent under control of the notify_classes configuration parameter.

The usage and specification of template message headers is subject to the following restrictions:

• Template message header names can be specified in upper case, lower case or mixed case. Postfix always produces bounce message header labels of the form "From:" and "Subject:". so type it however, Postfix will fix it for you 💅
• Template message headers must not span multiple lines. one line, one header, periodt.
• Template message headers do not support $parameter expansions. nope, not here 🚫
• Template message headers must contain ASCII characters only, and must not contain ASCII null characters.

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💜 TEMPLATE MESSAGE TEXT FORMAT 💜

The second portion of a bounce template consists of message text. As the above example shows, template message text may contain main.cf $parameters. Besides the parameters that are defined in main.cf, the following parameters are treated specially depending on the suffix that is appended to their name.

• delay_warning_time_suffix — Expands into the value of the delay_warning_time parameter, expressed in the time unit specified by suffix, which is one of seconds, minutes, hours, days, or weeks.
• maximal_queue_lifetime_suffix — Expands into the value of the maximal_queue_lifetime parameter, expressed in the time unit specified by suffix. See above under delay_warning_time for possible suffix values.
• mydomain — Expands into the value of the mydomain parameter. With "smtputf8_enable = yes", this replaces ACE labels (xn--mumble) with their UTF-8 equivalent. This feature is available in Postfix 3.0. ⭐
• myhostname — Expands into the value of the myhostname parameter. With "smtputf8_enable = yes", this replaces ACE labels (xn--mumble) with their UTF-8 equivalent. This feature is available in Postfix 3.0. ⭐

The usage and specification of template message text is subject to the following restrictions:

• The template message text is not sent in Postmaster copies of delivery status notifications. (the postmaster is nosy but not THAT nosy 🫶)
• If the template message text contains non-ASCII characters, Postfix requires that the Charset: template header is updated. Specify an appropriate superset of US-ASCII. A superset is needed because Postfix appends ASCII text after the message template when it sends a delivery status notification. so like, wide enough to hold everyone, okay? 💖

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🔥 SEE ALSO 🔥

• bounce(8), Postfix delivery status notifications
• postconf(5), configuration parameters

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👑 LICENSE 👑

The Secure Mailer license must be distributed with this software. fr, don't skip this part 📜

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🧚 HISTORY 🧚

The Postfix bounce template format was originally developed by Nicolas Riendeau. iconic origin story, honestly ✨

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🌟 AUTHOR(S) 🌟

Wietse Venema IBM T.J. Watson Research P.O. Box 704 Yorktown Heights, NY 10598, USA

Wietse Venema Google, Inc. 111 8th Avenue New York, NY 10011, USA

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aaaand that's the whole thing bestie 🎀 this was the BOUNCE(5) page from the File Formats Manual — so hey, if you were wondering where it lives, it's page 5, file formats section, and that's the whole glow-up. slay, go forth, and write the prettiest bounce templates the mail system has ever seen 💅💖🦋