Hi It might help the experts to know which ISP you are using. For example, Gmail has a tendency to keep/archive all your email that you thought was deleted in "All mail". Best, Agnes

My email goes through my website host at Fatcow. I cleared all the old emails on that.

Ok, I am not at all an expert, but I believe Fatcow is transitioning accounts to a new server. Would Fatcow have an answer for you or did you already try them? For example if both accounts still exist during the transition, and your old account is being accessed by Thunderbird, but your webmail access reaches the new files, then deleting on Fatcow might not help Thunderbird until you have Thunderbird is set to access the new ISP location. My apologies if you already did all that - just a suggestion. Agnes

Thanks. The problem was with my mailbox size at Fatcow. Easy fix to enlarge mailbox but it would've helped if Thunderbird made it clear that their mailbox wasn't the one that's full. I've only recently begun using Thunderbird so the coincidence made me think the issue was with that program.

I'm glad you have that fixed. Thank you for posting your solution, it may be helpful to others. Agnes