If the yahoo pop3 and smtp you are using does not work anymore, probably you are using servers like the following:
- Incoming server (pop3): pop.mail.yahoo.it
- Outgoing server (smtp): smtp.mail.yahoo.it
The issue is in that .it (or whatever you have). You need to change .it with .com and your mail client will function properly.
So the correct server are:
- Incoming server (pop3): pop.mail.yahoo.com
- Outgoing server (smtp): smtp.mail.yahoo.com