If you use Entourage, ignore this post.
To attach a file to an email, you can drag it to the mail icon. Mail will start a new message with the file attached. Nice. (Entourage does the same thing.)
When sending files to Wintellians, don't do this. Start the new message, then click 'Attach'. Select the file, and check 'Send Windows-Friendly attachments'. I don't know what it does, but it sounds good.
If you do the drag and drop thing, you won't get this option.
(I assume Entourage, as a Microsoft product, is Windows-friendly by nature.)
PS: Don't send 'Windows-Friendly attachments' to Mac people.