Seamonkey clogged by too much mail ?

[oldmaven]

I've gotten waay behind in archiving and deleting old mail, and SeaMonkey now shows over 40k mails in my main account--figure >50k all told, counting other accounts and subfolders. The program has gotten sluggish, but today seems to have jammed up altogether. I tried deleting batches of old mails, and that worked for a bit, but now it's stalled altogether. The cursor always has an hourglass on it, the message-list and message-content panes are blank (but the folder-list pane is OK), and nothing responds to the mouse or keyboard.

When the program is loading, it says "not responding" for a few minutes, then I get a message that a script is busy or stopped )chrome://messenger/cpmtemtcp,,amdg;ie/ks:674). Clicking "continue seems to have no effect, but clicking "stop script" gets rids of the "not responding" line but leaves me with blank panes, as described above.

How do I get out of this mess?

[oldmaven]

I forgot to mention: Running Win 10 Build 1703. Don't know which version of Seamonkey--it']s recent, but I can't access Help in Seamonkey to find the version number, and Control Panel's list just went blank.

[DanRaisch]

Do you know how the account is set up in SeaMonkey, as POP or IMAP?
Does the same thing occur if you launch the application in Mozilla Safe Mode? http://kb.mozillazine.org/Safe_mode

[Anonymosity]

Did you empty the trash and compact the folders after deleting all those messages? The junk does not really go away until you compact.