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Aliases, forwarders and catch-all (default address)

Purpose. Route mail for addresses that are not mailboxes, copy a mailbox’s mail elsewhere, and decide what happens to mail for unknown local parts — the cPanel “Forwarders” and “Default Address” features.

Behaviour.

  • Alias — POST /api/v1/domains/{id}/aliases { localPart, destinations[] }: one address delivering to 1–50 local or remote addresses. Stored as Postfix virtual_alias_maps rows (view v_virtual_aliases), effective immediately. An alias may not collide with a mailbox. Destinations of an alias may use the alias as envelope sender when authenticated (sender-login map). GET, PATCH (destinations, active) and DELETE on /api/v1/aliases/{id} read, change and remove one.
  • Forwarder — POST /api/v1/mailboxes/{id}/forwarders { destination, keepCopy }: attaches to an existing mailbox; keepCopy:true (default) delivers locally and forwards, false forwards only. Several forwarders per mailbox are allowed, and each is its own routing row, so the mailbox keeps a local copy if any of its forwarders has keepCopy:true; it forwards only when every one is false. GET, PATCH (keepCopy, active — false pauses the forwarder) and DELETE on /api/v1/forwarders/{id} manage one. Forwarded mail is SRS-rewritten on the way out, so it still passes SPF at the destination (SRS — sender rewriting for forwarded mail).
  • Catch-all / default address — PUT /api/v1/domains/{id}/catchall { destination }: mail for any non-existent local part in the domain goes to destination (Postfix @domain lookup). DELETE restores the default: unknown recipients are rejected at SMTP time (550), which is the safest choice for reputation. There is no “discard” option in v1.
  • Who may send as these addresses. The sender-login map is built from the same routing view as delivery, so it is not only an alias’s destinations that pass it. As configured, a catch-all’s destination may also be able to send as any address of the domain that is not a mailbox, and a forwarder’s destination as the mailbox that forwards to it; this is read from the configuration and not yet reproduced.
  • All three appear in the audit log with before/after snapshots.

Configuration. None; everything is data in Postgres.

Limits & edge cases. A domain routed to another server keeps its aliases, forwarders and catch-all in the database, but none of them applies until it is routed here again: v_virtual_aliases leaves them out. Forwarded mail is SRS-rewritten so it passes SPF at the destination (SRS — sender rewriting for forwarded mail). Alias loops are not detected (Postfix’s virtual_alias_recursion_limit stops them). Suspended mailboxes stop receiving via forwarders too. Aliases and the catch-all inherit their domain’s active flag; a forwarder follows its mailbox’s active and suspended state instead.