Outlook 365 (classic) freezes syncing subscribed folders via IMAP

Win 11 home, with all current updates.

Outlook 365 (365) Version 2510 Build 16.0.19328.20010) 64-bit; with all current updates.

ISP: telusplanet.net (which is Google, with limited functionality),

Servers: imap.gmail.com, port 993, SSL/TSL and smtp.gmail.com, port 465, SSL/TSL

Protocol: IMAP. I was using POP before without any problems for years.

The problem: When starting OL it downloads new mail messages OK. But after a while it freezes in ‘Synchronizing Inbox’ or rarely ‘Synchronizing Trush’ and does not download new messages from the server (which are visible in Gmail on Chrome) nor delete messages from the server, which were deleted locally. When this happens, to get it back, I need to shut OL down, wait, say 15 min, or longer, start it again and usually it is enough, occasionally I need to shut down and power the PC again. I have not uninstalled and reinstalled OL yet but am thinking of it.

I use IMAP to sync mail, and Sync2 for contacts, calendar, and tasks – that works OK.

I have tried just about anything possible, rebuilding profile, repairing OL, clearing cache, unlinking OneDrive, whatever I could think of, or what Copilot suggested, all to no avail. It is obviously very annoying. I believe, if it is happening to me, it must have had happened to others as well. It all started after switching from POP to IMAP.

Any suggestion will be greatly appreciated, Jan