There's not enough in your post to nail down a "do-this" cure. So out comes this shotgun.
http://www.mvps.org/sramesh2k/IEFIX.htm
Bob
Any image I email in any format will arrive corrupted. 20-80% of it will appear but then just blank space. This is sending from Outlook Express through a wireless router, cable modem. It works fine if I mail from the cable company's web site. Up-to-date WinXP on new PC. Seems like an Xpress problem. I've been going around with this for 6 months with no answers.

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