Yahoo email timing out

For decades, I've had a couple of Yahoo email accounts using POP3 in
Sylpheed. Sometime between this past Saturday afternoon and Sunday
morning, they started timing out. Like someone pulled a switch without
warning. Trying to figure out why, and what to do. I can access Yahoo
Mail, so it's not a pw problem.

Wondering if it might have something to do with IMAP, I added a couple
of new accounts. Those don't show any sign of timing out, but a test
email didn't arrive, so I'm not sure they're working at all. And the
Yahoo account entries in Sylpheed (IMAP) don't show any default
files under either account (Inbox, Sent, Trash, etc.).

Any ideas what might be going on and what to do? Thanks,

Gene G