After much trial-and-error, I have gotten Cryptx to work...mostly. Fine with or without mailto, but getting it to do the job properly is a matter of guessing over and over how to use it because...there's NO DOCUMENTATION. Apparently it won't work with multiple email addresses, cc/bcc, subject, etc. The plug-in site is auf Deutsch; my German is shaky, but it doesn't matter because ... THERE'S NO DOCUMENTATION. By the way, in case I didn't mention it, THERE'S NO DOCUMENTATION. In other words, you're on your own.
Also, if you're using RawHTML Pro, you have to bracket email addresses with [/raw] and [raw] to get CryptX to work.
Not ready for prime time any more than the abominable WP editor.