Found invalid data while decoding.at MailClient.Protocols.AirSync.AirSyncItemSynchronizer

Hello.

Since last few days I’m having issues with sending emails using OWA/365. Here is the extract from the log. Nothing was changed on the email server.

Any ideas?

eM Client 10.0.3530+f0b89b73a0 (Windows)
20:59:24 [email protected] [AirSync] MailClient.Accounts.ConnectionException: Found invalid data while decoding.

I had the same error today. This probably happend after I tried to add the Teams-Add-In (but Skype was added). I had to give Permission via the OAuth-Pop-Up for the Add-in.
I deleted then the Add-In.
Today I noticed that the calendar data from MS365 was no longer synchronized. With the same error as above from infoweb1.

I deleted the App access on my MS365-Account, as well the MS-Account in eM Client.
Then I setup the MS-Account again as a E-Mail-Account in eM Client. The pop-up for OAuth appeared, I confirmed and was switched back to eM Client. But the OAuth-Pop-Up didn’t go away. So I closed the Browser.

It works now, and eM Client was added again in the App Access-List in MS365, but still see the Error for eM Client:

In my case, the problems with calendar and contact sync started in October 2024 and I had to set up the MS account again at least 6 times so far.