"Too many concurrent connections opened." connecting to exchange online with EWS using Microsoft OAuth2

Question

Hello,

Able to successfully connect to outlook/exchange online with EWS using Microsoft Identity Platform.
But getting following exception:
"Too many concurrent connections opened., Cannot open mailbox (ErrorInternalServerError)"

This has started happening when using OAuth, which was not the case with basic authentication.

Also came across following issue, which discusses the same thing. Unable to figure out how to apply the solution on Rebex EWS library?
https://github.com/OfficeDev/ews-managed-api/issues/237

Can you please help?

Answer 1

Hello,

I tried to reproduce the issue described in the link you provided, but the issue did not manifest. We did a search what mentioned header "X-AnchorMailbox" from the same link is used for and it turned out it is used when you need to impersonate a user in certain circumstances. See this Microsoft document.

Are you using impersonation? Can you share more information about the issue? How can we reproduce it using our EWS component? Which server you are connecting to?

Comments

Hello,

that is exactly the same code I made based on your description. Just a side note what version of our component are you using?

On monday you can expect a version that uses X-AnchorMailbox header to try.

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We are using "2020 R2" version.

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Hello,

here you can download a trial version of our Secure Mail beta build with support of X-AnchorMailbox header.

https://www.rebex.net/getfile/764bc38b5b3941f3827e9ba320ad1d1c/RebexSecureMail-BetaBuild7486-Trial-Binaries-X-AnchorMailbox.zip

please give it a try and let us know whether it helps you.

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Thanks Pavel,

Tried with more that 20 connection, i don't see the issue.
Is their any flag which controls adding X-AnchorMailbox header or it will be added always?

How can we continue to use these binaries, as these are trial?

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Hello,

the X-AnchoMailbox header is added when impersonation is used. Without impersonation we have no mail address we can provide to the X-AnchorMailbox header value.

If you have active support contract, please let us know on support@rebex.net for full version of this build.