if I recall correctly Yahoo allows attachments up to 6 mb in size. of course they tack on an extra mb sometimes after you finish uploading it to be attached which I never understood. Most email boxes will take atleast that much, but if you file is larger than this I suggest using WinRar to pack up and split the file in to smaller chunks or upload it to a file host like Rapidshare or Megaupload and send the link they give you to woh ever you want to have the file.