Microsoft announced a while back that the end of EWS is coming for exchange online which means M365 accounts. They will start blocking EWS requests from October next year and only support access via Graph API. I understand the Thunderbird team are also working on Graph API support.

EWS EOL

Sure but as @ApeNo1@lemmy.world noted MS is ending support for EWS in M365 in less than 12 months! So it took them 18 years to release something that still doesn't fully work (no Calendaring support, WTF?) and won't even be usable by this time next year.

🤦

If it only supported outdated Exchange servers that would be one thing

The only Exchange server that ISN'T outdated at this point is the 4 month old Exchange Server Subscription Edition. All other versions are now EoL and have no support. So unless you have a very particular need to keep your EX environment On-Prem then you may as well migrate to EXO.

If you are already using EXO then Thunderbird's new EWS support will stop working next October.

So difficult to sync contacts and calendar

If only there was a well-defined protocol in a series of RFCs for that, AND people could use more than one protocol in a binary.

I have never had an issue for my clients.