whats that empty sender?? Can you show an example?

We have the same intermittent problem...

And I have reported it a while back.

We've provided multiple troubleshooting steps to one ticket with multiple same-day replies, and the results of our replication attempts in the other. Plus, there was a five day gap where we never heard back from you, not to mention we had a holiday in there. You asked about downgrading (which we normally do not recommend as we want to fix issues and downgrading simply eliminates them without us being able to adequately figure out what's going on) and we responded within 30 minutes of starting our day...and 2 hours later you opened the ER ticket. 

I point this out to demonstrate that we're not ignoring the issue, we are being responsive, and to help you understand that customer-specific issues are much more difficult to resolve unless we can replicate them in house. This allows us a greater flexibility when diagnosing what's going on. Seeing it on your server is fine, but there is so much that goes into customer environments it takes time to troubleshoot issues.

Ok, other customer with the same problemm so the problem is not my server.

We are waiting now your solution.

Nope. Outlook is running fine and its intermittent. Days can pass and then it shows up out of nowhere.

Are the messages where the problems occur signed with SMIME? I sometimes encounter these problems with SMIME-signed messages.

All the mesage are affliceted, if delete the outlook cache the sender appears but the new message are empty.

I try oulook 2021,2024 (MAPI configuration) same problem... the problem is only for new message, when i see them in the outbox folder the sender is missing, but if i check in webmail i see it.

All users with outlook mapi are afflicted

If i send the email from my phone in outllok i see the sender corretcly, after delete the outlook cache, when i close outlook and reopen the sender appears.

Its exactly the behaviour I have reported. But for us its intermittent not permanent.

We are experiencing exactly the same behavior (empty sender), but as far as we can see, only with messages that are signed with SMIME (90% of the emails we use are signed with SMIME). In this context, we also occasionally have the problem that an error window appears with the message “Unable to connect to the server.” Outlook always has to be restarted, after which it usually works. 

Please note that in our case, if the sender is empty, the entire message is empty for the recipient.

Unfortunately, a ticket did not help us, as ST was unable to reproduce the problem.

We tested everything: clearing the cache, recreating the profile, using a different PC, deactivating the virus scanner on the client and server, checking the firewall, but unfortunately without success.