Mac Mail not Synchronizing with Gmail IMAP Server, Tahoe OS

Do a SafeBoot Start up your Mac in safe mode - Apple Support will sort many anomalies

Login and test. Reboot as normal and test. Caches get rebuilt automatically.

You could try removing the gmail account and re-enter it in Mail. Make sure that you have your password available just in case the server asks for it.

I’m seeing two related issues on macOS 26 (Tahoe).

First, my Mail rule that moves messages from my Gmail inbox to an iCloud mailbox doesn’t run automatically — it only works when I trigger it manually.

Second, when I use an AppleScript (I was trying to troubleshoot the rule) to perform the same action (moving Gmail messages to iCloud), I experience the same sync problem that Steve Solomons described: the messages are moved successfully to iCloud and disappear from the Gmail inbox in the Mail app, but they remain on the Gmail server and still appear on my iPhone.

The only difference between my setup and Steve’s is that I’m moving messages to an iCloud mailbox instead of an “On My Mac” folder.

this is the script I'm using:

on idle
	tell application "Mail"
		try
			-- Access the "All Mail" mailbox of your Gmail account
			set targetMailbox to mailbox "[Gmail]/All Mail" of account "Personal"
			
			-- Access the iCloud mailbox
			set iCloudMailbox to first mailbox of account "iCloud" whose name is "CCA 2025-Now"
			
			-- Find messages with "[Nagleepark-CCA]" in the subject
			set targetMessages to messages of targetMailbox whose subject contains "[Nagleepark-CCA]"
			
			set messageCount to count of targetMessages
			
			if messageCount > 0 then
				-- Move messages one at a time with 2 second delay
				repeat with i from 1 to messageCount
					set msg to first item of (messages of targetMailbox whose subject contains "[Nagleepark-CCA]")
					move msg to iCloudMailbox
					delay 2
				end repeat
			end if
			
		end try
	end tell
	-- Return 60 seconds (1 minute) before running again
	return 60
end idle

I have the same problem. A call to Apple Support was no help. I have also filed a bug report with Apple. My work email is hosted by Google. The use of rules is essential to get through the 200-400 emails received everyday to the 25 or 30 I actually need to look at. Mail has been worthless since the "upgrade" to OS26. I've tried the suggestions shown here with no luck to date. This is a serious issue Apple needs to get resolved quickly.

Is Apple aware of this issue with MacMail?

Make the server settings in Mac Mail are correct (IMAP: imap.gmail.com, SMTP: smtp.gmail.com)

Are you on as Google puts it "premium versions of Gmail, Calendar, Drive, Meet, and more." because it is slightly different that the Regular Gmail that I use and I haven't seen how it is set up.

I keep getting imap timed out errors - happens with icloud as well - not sure deleting and re-adding the accounts will work? Has anyone found a solution?