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Mail server integration#

This documentation applies to Piler enterprise edition 2.2.4+ and piler-smtp 1.1.6+

Revision #1

Publication date: 2026-OCT-17

Overview#

Your mail server sends a copy of every incoming and outgoing email to piler-smtp by SMTP. To archive the Bcc recipients as well, it encodes each recipient of the email in the archive address it sends the copy to:

<tenant>+<recipient local part>=<recipient domain>@<archive hostname>

customer1+anna=customer1.com@archive.example.com

piler-smtp decodes the recipients, and Piler archives them like the To and Cc recipients. How it works and how to set up Piler for it is described in Envelope recipients.

The guides below show the mail server side.

Mail server Method Guide
Postfix recipient_bcc_maps and sender_bcc_maps Envelope recipients
Axigen Acceptance & Routing rules, Add recipient action Axigen

What every mail server needs#

  • One copy per recipient's archive address. The mail server has to produce the encoded address for each recipient, Bcc recipients included. Ideally all the addresses of an email go to piler-smtp in one SMTP transaction; copies that arrive separately are merged within ENVELOPE_MERGE_WINDOW_HOURS (24 hours by default).
  • Access to piler-smtp. The encoded addresses grant access to emails, so piler-smtp must accept email only from your mail servers: restrict it with a firewall and with its access list (smtp_access_list=1, /etc/piler/smtp.acl).
  • TLS. If the mail server verifies the certificate offered for STARTTLS, piler-smtp needs a certificate it trusts, e.g. one issued for the archive hostname.
  • No archive address as a recipient. The archiving rules must not apply to the archive addresses themselves. Since 1.1.6 piler-smtp ignores an archive address of its own hostname encoded again, but not one of another archive host (e.g. a DR site), so the rules have to exclude those.