Thanks a lot for this clarification.
We contacted our ISP, this is their intentional drop, the don't want to
deliver any mail with empty 'From' field, we cannot do anything with it.
We need to send NDR though ;)
Is there any way to configure OpenSMTPD to send NDR using another SMTP
relay, or directly? Ideally - send *_all_* NDR directly, but we can list
the destination addresses too (as 90% of mails that can /potentially/
produce NDR are from limited list of addresses, managed by our internal
app).
Peter
On 30/09/2024 17:34, Stuart D Gathman wrote:
On Mon, 30 Sep 2024, Quelrond wrote:
It seems that OpenSMTPD sends non-delivery reports with blank 'From'
field. Our ISP relay does not like it. Is there any way to put a
'correct' smtp address to use for NDR sending?
Empty MAIL FROM is the only correct way to send NDR. If the sender
doesn't like NDRs (or are just broken), then just drop the NDR. On
sendmail, I had a per sender policy using SRS to send the NDR disquised
as a reply with a special localpart to prevent loops.
The RFC defines empty MAIL FROM as equivalent to postmas...@example.com.
The empty MAIL FROM prevents an NDR to an NDR. The postmaster mailbox
MUST be deliverable, so if you absolutely have to accomodate broken
senders for business purposes, use a special mailbox like
n...@example.com that refuses all attempts at delivery at MAIL TO
(envelope stage).
