I would verify that their Exchange account is the only account within outlook. From a few different places it looks like it could be something stuck in Drafts too (although you said you checked there). Possibly removing the account and re-adding it in Outlook could be the quick fix to it (although they would lose their saved autocompletion which a lot of people complain when they lose it).
Error Code 19803 Microsoft Outlook Mac Download
Im running 2016 on probably 25 Mac's and haven't seen this issue yet, but I have had weird issues with Outlook in general that aren't worth the time messing with and just adding the account back again will fix saving all of our times.
Error Code 19803 Microsoft Outlook Mac 2017
Error Code 19803 Microsoft Outlook Mac Excel
My Microsoft Outlook office 2011: for mac is not connecting to my exchange server. It worked when I installed, and stopped the next morning, spend 3 hours trying to solve the issue, and even ended up uninstalling, the program twice. Code 19703 and still not downloaded this update, then install it as soon as possible. What Do You Mean. 2018-3-13 A remote code execution vulnerability exists in unpatched versions of CredSSP. An attacker who successfully exploits this vulnerability could relay user credentials to execute code on the target system. Icloud outlook add in download. Any application that depends on CredSSP for authentication may be vulnerable to.