NethServer Version: 7.9.2009
Module: Email
Hello everyone,
I think, I need a mental nudge 
.
The following scenario: Exchange Server 2019 on-prem multidomain, send connector to NethServer with 3 relay hosts created (one relay host per domain), mail dispatch to provider IONOS. So far, so good.
Now I have noticed that the out-of-office messages to external senders are no longer going out. Error message from IONOS: “550-Requested action not taken: mailbox unavailable 550 Sender address is not allowed.”. From IONOS’ point of view, this is correct, as emails with empty senders are no longer accepted. According to the RFC specification, these out-of-office messages must be sent with an empty sender. I can’t get any further with IONOS support, so I have to find another solution.
My assumption was, that if none of the 3 relay rules apply, then the setting for the default relay host (“smart host”) applies. The smart host is also configured, but obviously this has no effect if the sender address is empty.
Surely it is somehow possible to give the sender “from=<>” a real sender address. Does anyone have any ideas?
Thanks in advance & best regards
Alex