Mail Server (5)

• Postfix - ArchWiki (wiki.archlinux.org) tutorial
  setting up Postfix on Arch: main.cf and master.cf, aliases, local vs virtual user delivery
  Arch Linux Email #
• Home | Dovecot CE (doc.dovecot.org) reference
  IMAP, POP3, LMTP and ManageSieve server docs for the open-source Community Edition; Pro is commercial
  Commercial Support Email #
• OpenSMTPD (opensmtpd.org) tool
  OpenBSD's server-side SMTP implementation of RFC 5321, small and auditable, ISC licensed
  BSD Email #
• Rspamd — Email Security System (rspamd.com) tool
  Async C spam and phishing filter: regex rules, RBLs, greylisting, SPF/DKIM/DMARC/ARC, ML scoring
  Email Spam Filtering #
• OpenDKIM (opendkim.org) tool
  C library plus milter giving sendmail-compatible MTAs DKIM signing and verification, also VBR and ATPS
  Email Spam Filtering #