Out of the blue, since this morning, whenever I send an email from the domain dooms.eu (served by mailcow) I receive an error message:
Your message did not reach some or all of the intended recipients.
Subject: FW: Test
Sent: 6/26/2023 3:24 PM
The following recipient(s) cannot be reached:
Luc Dooms | Agio Capital on 6/26/2023 3:24 PM
Server error: '451 4.3.0 firstname.lastname@example.org: Temporary lookup failure'
Restarting SOGo does not help.
What can I do?