qpsmtpd

[2008-11: New installation on 10.3/8.6.0]
[2007-04: Implementing SMTP Authorization with qpsmtpd running under SuSE 10.0 and Plesk 8.0
[2014-01: Here's an update to these instructions.]
[2018-09: Update #2 on Installing qpsmtpd on Xenial, completely replaces 2014-01]

[2008-11: New installation on 10.3/8.6.0]
[2007-04: Implementing SMTP Authorization with qpsmtpd running under SuSE 10.0 and Plesk 8.0
[2014-01: Here's an update to these instructions.]
[2018-09: Update #2 on Installing qpsmtpd on Xenial, completely replaces 2014-01, replaced by the following]

This is an update to my original instructions for installing qpsmtpd on a Linux system running under Plesk.

Just in case you don't have cc yet:

apt-get install build-essential


qpsmtpd is now on GitHub

qpsmtpd's README mentions installing the following "required Perl modules"

perl -MCPAN -e 'install Net::DNS'
perl -MCPAN -e 'install MIME::Base64'

For a while now I've been getting a Chinese piece of spam every day, supposedly sent by people like 魏碈, which is encoded as

From: =?utf-8?B?6a2P56KI?=

These pages have helped make sense of this:
BASE64 Decode and Encode
Wikipedia: Base64
UTF-8 encoding table and Unicode characters
RFC 2044 (UTF-8)

Receiving incoming email and making it available to your users via POP3 or IMAP is only the first half of running a Message Transfer Agent (MTA). The other half is to relay outgoing email from your users to the world.

We don't want to run an open relay, of course, so we we need some form of authorization.