Unable to sync comcast email across iphone, ipad and desktop. This setup has worked for 3+ years but now have to frequently reset.

For last 2 months, have encountered numerous fails of syncing across devices, after 3+ years of seamless use.  Desktop continues to work fine, but iphone and ipad don't sync. Have tried numerous solutions (deleting and adding the email account, forcing restart on the devices, checking for update on the Mail app, etc.) and nothing seems to stick for more than a few days. This is incredibly frustrating. Is there a solution that will solve this?