What are your account's server settings for leaving messages on server?

Leave messages on server until I delete them. But I've also tried unchecking that box and problem persists.

Are they never deleted, or is it a time-delay issue? I'm thinking it may be a PC-to-server issue that delays the appearance of the deletion.

How long would you wait before deciding "never?" They're certainly not deleted almost instantly as they are when deleted from my phone, and still not deleted after several minutes.

Okay, how many minutes after clicking delete? I was attempting to get a feeling for the severity of the issue. The connection workflow from PC to server is likely different from cell phone to server.

Well, it's been about 50 minutes and still not deleted.

I wonder if it deletes on the next 'get mail' request. That would make sense for POP. Please try that.

It works if I delete on PC, then do get mail on web and again on PC. Sometimes I have to do this more than once.

Here's another quirk: If I've downloaded new messages on both my PC and the Web server and then delete from the Web server, the message remains on my PC. But it I delete from the Web server before I download new messages on PC, they don't show up on PC. But on my phone, even when I've downloaded new messages on both it and the Web server and then delete from the Web server, the message is deleted on my phone when I check for new messages.

That signals to me that the phone is IMAP. That would explain that a message deleted from server is deleted from phone.

You're right! I never noticed that. But the incoming mail server on the phone is pop3.comcast.net. Can that be? So if I changed my PC to IMAP, should I be able to delete both ways, i.e., deleting from PC deletes from server and vice versa?

With the last update for TB, deletes became very slow. It seems to be involved with the copying of files to the trash folder. I just did a clean up of my inbox on two computers. Had 600 on notebook to delete and almost 900 on my tower. Before the last update, 100 deletes would be almost instantaneous. Trash was empty and the HDD are both SSD's. Made sure all temporary files had been removed from each and they were both clipped for fast processing. It took 45 minutes on the tower and 2 hours on the notebook. Also did a file compress before starting the delete process on all TB files.

Please take note....This extreme slow down for deletes came with modifications to the current version of TB.

Never had a process like this take this amount of time in last 30 years.

If the server is POP, then we're not seeing what is happening. The server's delete does not affect a POP client. The only way for both phone and PC to be in total sync would be if both are IMAP. Then, when one deletes a message, it is not visible anywhere. And when one responds, it is visible in both places.