An internal server error occurred. The operation failed using EWS and OAuth with Office 365

Question

We have recently converted to using OAuth with Exchange Online from Basic Authentication.

Just starting today, a number of customer sites reported the following errors, sometime intermittently:

Rebex.Net.EwsException: Internal server error. An internal server error occurred. The operation failed. ---> Rebex.Net.EwsException: Internal server error. An internal server error occurred. The operation failed. ---> Rebex.Net.EwsException: Internal server error. An internal server error occurred. The operation failed.

In some cases this is intermittent and in other cases it is regularly reproducible. The strange thing is that this has been working properly for the last week or two since our customer started using OAuth.

Any assistance would be much appreciated.

Comments

I'll send you a verbose log once colleagues get it, so we might get further. Since there is no diagnosis it might be problem in Rebex or in Microsoft API, so we have to work on both ends :-). In fact we can serve only as mediator between you and Microsoft - we are not experts on EWS or O365 - that's why we use Rebex lib - otherwise we could use directly MSFT libs.

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Sent logs to support email address. Problem has 100% repro on our internal company test account.

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It really looks like this is a Microsoft issue. Non-Rebex users are encountering the same problem as well: https://docs.microsoft.com/en-us/answers/questions/980333/internal-server-error-connecting-to-o365-exchange.html

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I checked Jiri's log, and it appears the same as ITM's log and our logs... App-only authentication, "500 " HTTP error on first GET request in the Login method, with "ErrorInternalServerError" code in the SOAP response (just like in the link above).

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What has been the longest period observed between the first appearance of "ErrorInternalServerError" for a particular mailbox and its disappearance? In case of mailboxes where we reproduced the issue, the outage only lasted for a moment. But for the users of Microsoft's library at the link above, it seems to persist for longer periods as well.

Answer 1

This seems to be server-side issue. Microsoft's EWS service has been apparently having some troubles recently, and non-Rebex EWS users are affected as well. More information: https://docs.microsoft.com/en-us/answers/questions/980333/internal-server-error-connecting-to-o365-exchange.html