Hello there and welcome to lfete at Fixya Support Team

you can find the normal messenger at your pone accessories here in the manual at page 116 :
http://www.kolyasoft.com/pocketpc/imatejam_ppc_userguide.pdf

you can find yahoo messenger for Ipone here :
http://messenger.yahoo.com/platform/iphone/

you can find one in all messenger here :
http://imate-jam.handster.com/im_allinone_messenger_for_wm_pocket_pc.html

I can see that there is also a chat session inside yahoo mail, maybe you can start using that. I do not know if this are the same as yahoo messenger

Hope that helps
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Have a nice time over there
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