The only yahoo messenger client for Pocket PC I found is an old old version (for wince 2.11) http://messenger.yahoo.com/messenger/ce/downloads_ce_msgr.html
I can connect sometimes, but the software seems to close itself :?
I don't know if yahoo developers plan to develop a updated version ?
Would be great as all my contacts are under yahoo messenger.
visit www.yahoo.Co.uk click on the messenger link then look at the left of the screen. there is a link to wincE versions and open that will show you 2 versions. 1 for ppc 2002 and 1 for older wince versions.
However the problems listed above regarding servers and ports should be noted.