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--- ssh_sendmail_instead_of_login_shell [2022/11/12 17:34] – added conclusion paragraph jquah
+++ ssh_sendmail_instead_of_login_shell [2022/11/13 23:41] (current) – delete --- to be recreated with a more accurate name jquah
@@ Line 1: / Line 1: @@
-==== SSH session that runs sendmail instead of an interactive shell ====
-=== What? ===
-A wrapper for your local mail transfer agent (MTA) that initiates an SSH session when your SDF email address appears in the "From:" header.
-=== Why? ===
-You want to send email from your SDF address without running the risk that the receiving server will reject it due to a mismatch between the "From" header and your ISP's IP block, but ...
-  * the low volume of your outgoing mail cannot justify the cost of a VPM/VHOST/MetaARPA membership, or
-  * your Internet connection has too high a latency to be running a full-screen editor within an SSH session.
-=== Where? ===
-a *BSD, Linux, or WSL environment with a client that generates MIME-formatted mail (as expected by sendmail-compatible MTAs such as msmtp)
-=== How? ===
-  - Set up [[ssh public key authentication|SSH public key authentication]], if you have not already done so. This step can be omitted if you prefer to type your password for each outgoing mail.
-  - Save the wrapper script below somewhere in your $PATH. Change the value of $MTA to the mail transport agent that you would otherwise be using for outgoing mail, the value of $PATH if any of the commands live in non-standard locations, and of course all the hard-coded email addresses in the script.
-  - Configure your mail user agent (MUA) to call the wrapper script, rather than calling your MTA directly.
-<code>
-#!/usr/bin/env bash
-#
-# msmtp.wrap - bypass local in favor of remote sendmail,
-#              if certain headers are found
-PATH=/bin:/usr/bin:/usr/local/bin
-Account0=me@sdf.org
-Account1=me@other-pubnix.net
-MTA=msmtp
-draft="$(mktemp -t sendmail.XXXXXX)"
-cat /dev/stdin > "$draft"
-sender="$(grep '^From:' "$draft" | head -n 1 | cut -d: -f2)"
-case "$sender" in
-    *me@sdf.org* )
-        sendmail="ssh $Account0 sendmail -t" ;;
-    *me@other-pubnix.net* )
-        sendmail="ssh $Account1 sendmail -t" ;;
-    * )
-        sendmail="$MTA $*" ;;
-esac
-< "$draft" $sendmail; status=$?
-rm -f "$draft"; exit $status
-</code>
-=== What Next? ===
-The possibilities for customization of this wrapper are only limited by your imagination. You can parse the outgoing messages to look for particular recipients, subject lines, etc., and define a custom $sendmail command to handle each case. On the SDF side, the command is being passed to your usual login shell after the ''-c'' option, so you will enjoy all the environment variables defined in ''$HOME/.bash_login'' if you use bash as your login shell. Save your custom scripts in a directory that your SDF login shell considers part of $PATH, and you can then perform all kinds of tasks (like updating your website) without leaving your mail client.