Chris writes:
>  -md5 is NOT unbreakable;

As far as I know, md5 should still be as close to unbreakable as you
would ever want.  If you don't trust md5, then you can switch to SHA
or some other cryptographically secure message digest algorithm.
Unfortunately, you can easily attack the *protocol* rather than the
*algorithms* used, because:

> Client generates a hash code from a combination of the welcome
> banner and the (mailbox) password. Client sends the user name and
> the hash code to the server.

If Eve can monitor both sides of the connection then she can take the
welcome message and the hash sent back to the server and then go off
in a corner and guess passwords until she finds the one which generates
the right hash value.  This is the same process as cracking passwords
out of a copy of an /etc/passwd file.  It means that the resulting
system is only as secure as the pop3 passwords the user chooses (or is
assigned).

An encrypted login process is not of much value if the actual
session will be conducted in the clear once the user is authenticated,

G.