Problem with emails from Mac Mail with attachments

[CountryMom27]

I'm not an android user - my colleague is, and thus this is causing me a headache. Aside from some tylenol, I'm hoping you can help me.

I use a MacBook with Snow Leopard and Mac Mail. When I send an attachment to his account, if he gets it on his PC, all is fine (I have Mail set to send windows-friendly attachments). If he gets it on his Android, the message is garbled, attachment fine. If I send the same exact email from a web-based email system (e.g. DeskPilot), it's fine.

Has anyone run into this? Suggestions? I assume something is wrong with my settings or there's some sort of conflict with Android?

Thanks very much1