- The "From" should not be the administrator user but
the postmaster/system, and should be an address that
ignores double-bounces. Using the default bounce
email accomplishes both.
- The "To" recipient should be the "envelope from"
sender when available, usually as provided by
the "Return-Path" header set by the upstream MTA.
If not present, fall back to the "From" of
the original email.
- adapt tests to verify the behavior wrt Return-Path
Olivier Dony
74d8cbc190