Pls check if the mailbox that you are trying to send the mail from is not marked as Postmaster? You can do that in Email and Conferences >> Settings >> Mail and Conference Settings >> Postmaster field
Hello,
We also have a customer on windows who is on 2026-02-28 having the exact same error message after updating.
The title of the messagebox is in our case is: "C:\Program Files(x86)\Han...
