Empty SMTP FROM doesn't mean it's a DSN. It means you don't want to receive
DSNs.
Autoresponses often don't want to receive DSNs, so a empty SMTP FROM is
appropriate
Paul
On 21 November 2025 08:29:03 Paul Menzel via mailop <[email protected]> wrote:
Dear Mail Operators,
While looking more into into unsolicited emails from
outbound.protection.outlook.com (Microsoft 365(?)), we noticed often
away messages are sent with an empty SMTP FROM. Are such messages really
delivery status notifications (DSN)?
Kind regards,
Paul
PS: Example for dtu.dk with subject
Automatic reply: …
[…]
Nov 21 08:46:20 mgw6-erl postfix/smtpd[1471745]: C7687600F5:
client=mail-westeuropeazhn15013015.outbound.protection.outlook.com[52.102.161.15]:49673
Nov 21 08:46:20 mgw6-erl postfix/cleanup[1463488]: C7687600F5:
message-id=<cb4806352120417382865636c0b78...@paxp192mb1462.eurp192.prod.outlook.com>
Nov 21 08:46:21 mgw6-erl postfix/qmgr[3982567]: C7687600F5:
from=<>, size=12160, nrcpt=1 (queue active)
[…]
$ host dtu.dk
dtu.dk has address 52.236.166.178
dtu.dk mail is handled by 0 dtu-dk.mail.protection.outlook.com.
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