Hotmail message and calendar sync solution? (AirSync)

eM Client worked well until early autumn 2024. But after an update I could no longer send emails (they would simply stay in the outbox) and no item I entered in the calendar would sync across.

Then, without any update that I can spot (I hadn’t run either a Windows update or an eM check), on 26/2/25 everything sync’d and I got a pop up error log. Now everything worked great.

Today, back to emails getting stuck in the outbox.

I can see plenty of other users experiencing Airsync issues for years now. I assume eM Client must have seen error logs but in case not, and in hopes this log can help resolve the issue promptly and permanently, here is my error log.

Without a resolution I’ll need to give up on eM Client, despite everything I like about it.