Encrypted Mail

[Guy Harris]

>At least on Sun systems we have here, there is a facility to do this. I
>believe this only works on local mail. here is most of the man page.
>
>NAME
>     xsend, xget, enroll - send or receive secret mail

This dates back to V7, although it wasn't picked up by the S3/S5 side of
the house.  Since it was in V7, it's in 4.xBSD; it may also be in
commercial systems other than Suns....

It does, in fact, work only on local mail, since it delivers mail by
writing to a file, not by handing it to some program such as "sendmail"
cognizant of SMTP or other network mail delivery protocols; you may be
able to make it work over NFS or some other network file system, though,
with a shared "/usr/spool/secretmail" directory (although since the
notification is sent by ordinary mail, the recipient needs an account on
the local machine anyway, or at least an alias to get the mail to them).