Can Yahoo Mail work with Outlook over IMAP
Well, it used to! However, it seems that IMAP support was always a beta program, and thus not supported.
It does seem that Yahoo operate IMAP servers at imap.mail.yahoo.com port 143, and imap-ssl.mail.yahoo.com for SSL port 993. However, you need to add a non-standard command string in your mail client for Yahoo to talk to it.
Of all the places to look for it, I didn’t think there’d be a dedicated Wikipedia article, but there is:
However – whether there’s a trick for this specifically in Outlook (2003), appears to remain elusive.