Strange exception from the Exchange Web Services "An internal server error occurred.

[Arrow312]

Recently we started to get strange exception on the EWS: SyncFolderItems call, this is the error : "An internal server error occurred. The operation failed., IdAndSession.MailboxSession: session is not IMailboxSession". 

Please note that code didn't change for more than year.

All those issue are on customer accounts, we had this in the past and after sometime those errors vanished, but we need to figure out what is going on. We notice that this someone have the same issue here:https://social.msdn.microsoft.com/Forums/office/en-US/ee750676-24a9-4aa4-bbdd-43cf2c9ff813/ewsexchan... . It's related to exchange version update. Therefore, can anybody help me to review this issue?

[#2]

Hi,

This is what I have , looks like its a bug and Microsoft is working on it. there are many people reported this and talked to MS and they have got the same answer that "its a bug"
Please refer this forum below and let me know if this helps!

https://stackoverflow.com/questions/48950767/ews-findfolders-throws-an-internal-server-error-occurre...

[#3]

Same issue here, it's already a week with this strange error, and Microsoft support doesn't provide any meaningful answers, only that they don't support 3'rd party applications and that it's a connectivity issue. Very non-professional. 

[#4]

It should be fixed now. {Version: 15.20.1446.019}