I'm a long time Yahoo Mail user. Just to illustrate how long I've been with them: when I joined the space available was a couple of MBs! I staid with them because I was mostly satisfied (never really caught the GMail bug), however recently I started looking for options to consolidate the different email accounts (work / personal / yahoo / gmail / etc). I explicitly wanted IMAP support because I really need to keep in sync between multiple machines.
The common wisdom seems to be on the 'net that Yahoo! Mail doesn't support IMAP (not even for paid accounts) or that various hacks are needed to support it (like sending custom / non-standard commands after login). This information however seems to be outdated, since I was able to find a least 3 IMAP servers (I've tested them all and they all work - with standard email clients with no hacks!):
- imap.mail.yahoo.com (this is the one Thunderbird configures by default)
- winmo.imap.mail.yahoo.com (from this article)
All of the servers support SSL/TLS encryption, so they are safe to access even from public hotspots. The outgoing server is smtp.mail.yahoo.com, which also supports SSL/TLS (and you should use it!)
The easiest to set up is Mozilla Thunderbird, however Evolution seems to work much better. One important feature in particular is that it works with large (10 000+ emails) folders, while Thunderbird chokes with an error ("UNAVAILABLE] UID FETCH too many messages in request"). To have Evolution work properly, you need to select "IMAP+" (also called IMAPX) as the protocol.
HTH somebody out there.