Can't Import Old Email Messages from ATT Mail

I have a Mac Mini 2018 running Ventura (13.2.1). Prior to sometime last year (as best as I can remember) my ATT email account in Apple Mail had messages going back at least 10 years. Now the oldest message is from April 2022. I have other accounts in my Apple Mail setup, all with messages older than that (and back as far as 2011). I can see the older messages on the ATT/Yahoo mail server when I use their web interface, going back to 2011.

I have tried rebuilding the mail box, and re-importing mail after deleting the Envelope Index files in /Library/Mail/V10/Mail Data. Each time I get the same legacy messages back only to April 2022. BTW, I see the same limited history on my MacBook and iPhone.

My other email accounts are Microsoft Exchange. I have my ATT mail set up as IMAP.

Any suggestions on how to get the older messages to sync with Apple Mail?