From time to time, I receive email with an empty message body and an attachment named smime.p7m. How do you deal with these on a Mac? Such attachments are cryptographically signed messages, and possibly encrypted -- though encrypted messages may have a different extension. Signature verification or decrypting seem to be very hard on the Mac. However, the message is just probably just signed and not encrypted.
To view it on your Mac, drag the attachment to BBEdit. If it's signed and not encrypted, after a few garbage (binary) characters, the whole message text will be readable. I copy that text to the clipboard, go back to Eudora, make the message editable, and paste the plain text into the message for later reference. As an aside, does anyone know how to verify cryptologic signatures and/or decrypt these attachments?
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070522064027293