Get Exchange Mail Message sometimes doesnt work

Hey I have a problem with the “get exchange mail message” activity.

I have an automation which gets mail messages and sorts them in folders via move mail message.
What I dont understand is that I sometimes get the error message “The SMTP address has no mailbox associated” and sometimes I dont.
Most of the times my automation works until like 9 am and stops working after 10 am and I dont understand how this is happening.
Do you guys have any ideas what could go wrong?

Hello, @Fabi99v - Have a look on the below thread. Try to specify full domain in the user name

Thanks for the reply. I defenitly fullfill these requirements. I have my username set as “” and the mailbox exists for sure.