Never used Prime, so I'm not sure of its export capabilities. If you can export the mixes as MP3s, that would be easiest. If not, export the mix down as a type of file that can be opened on most players, e.g., a WAV file at 44.1 kHZ & 16-bit, or export the mix down in a format you can open in iTunes (e.g., the aforementioned WAV file, or an AIFF) and in iTunes, convert the files to MP3s, then export those MP3s as attachments to your outgoing mail.