Exchange message transport & routing has at times been a bit challenging to understand. Whether it was the X400 based Mail Transport Agent (MTA), Open Shortest Path First (OSPF) based routing in Exch...
Updated Aug 23, 2023
Version 9.0
Blog Post
This is an older Blog but nevertheless I will try to get an answer 😉
We are routing all in- and outgoing mails (from and to Exchange-Online) through our FortiMail Mailgateway with partner-connector. The Exchange OnPrem is only for management without mailboxes, but there is still the "Inbound and Outbound-OnPrem Connector" enabled with TlsDomain '*.ourdomain.com' created by the HybridWizard.
Our issue is:
- We activate on the Fortimail the smtp certificate for outgoing emails , the certificate is '*.ourdomain.com'
- After that, every outgoing email where the recipient is also in Office365 (a.e. mailto:Email address removed), is ending up in a mail loop until the hop count reaches its limit.
Is that because of the above mentioned "Inbound or Outbound-OnPrem Connector" enabled with TlsDomain '*.ourdomain.com'? Is one of them taking over the emails destined to a totally other tenant?
How can I find out which connector is the problem? Trial/Error?
Thanks 😉