I've received some questions about how to best encode files attached to Eudora messages recently, so I thought I'd reiterate the information in Eudora itself about this topic (turn on balloon help and point at the options in the Attachments section of Eudora's Settings dialog box). The commercial version of Eudora offers four settings: AppleDouble, AppleSingle, BinHex, and Uuencode. The free version of Eudora lacks Uuencode support, and is available at:
Use AppleDouble when sending files to other MIME-compatible mailers. AppleSingle seems to be unusual - Steve Dorner says that it's acceptable for Mac-specific files, but notes wryly in the balloon help that only "a few whackos need this." BinHex is the standard in the Mac world and is the safest for sending files to other Macs, particularly if the recipient uses an older mail program. Uuencode is best for communicating with archaic mail programs primarily on non-Mac platforms (Microsoft Mail, for instance, used, and may still use, uuencode for attachments). For more general information, check the Eudora 1.5.1 documentation and Q & A stack at:
So in standard use, if you're sending mail to people who definitely use Eudora or other MIME-compatible mailers, even on a PC, use AppleDouble. If you're mailing Macintosh files, they're probably destined for Macintosh users, so if you're unsure about what the recipient might use to read email, BinHex is the safest. And finally, if you know the recipient uses DOS, Windows, or Unix and an old email program that doesn't support MIME, you should go out and ante up your $65 for the commercial version of Eudora so you can easily use Uuencode. You can read a bit more about MIME and these issues in the relevant Request for Comment (RFC), #1741.
Frankly, if you seriously use Eudora and email, the commercial version's cleaner interface (like being able to sort a mailbox by clicking in the column title) and massively useful filtering capabilities make it worth a measly $65. Besides, I strongly approve of Qualcomm keeping a version of Eudora free for people who don't use email heavily or who want to try Eudora, and buying the commercial version is the best way to support Qualcomm's attitude toward the free version.
Qualcomm recently set up a mailing list Eudora discussions. To subscribe, send email to <firstname.lastname@example.org> with "subscribe mac-eudora-forum" in the body of the message (sans quotes, of course). Make sure that your return address is correct - it is the address that will be added to the mailing list.
Qualcomm -- <email@example.com> -- 800/2-EUDORA
619/597-5113 -- 619/597-5058 (fax)