Windows Mail and Outlook Express let you add some spice to your outgoing emails with background sound. Unfortunately, not all music files are supported for this feature. You can't use sound encoded in mp3, AAC or ogg vorbis, for example.
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Formats Supported for Background Sound in Windows Mail and Outlook Express
Here's the list of what is supported for background sound in Windows Mail and Outlook Express:
- .wav, .au, .aif, and .snd wave files
- .mid and .rmi MIDI files
- .ra, .rm, .ram and .rmm Real Media files

