The fact that you're already doing Xish stuff in your server makes me wonder if it wouldn't be more sensible to build the whole xbiff functionality into it.

Alternatively can you run the xbiff on a machine which is allowed to see the mail spool directly?

pop-agent isn't doing X intrinsically; it's spawning an xterm to ask for the password. (At some point I hope to switch this to ssh-askpass, but when I originally wrote pop-agent it was running on a machine that didn't have that installed.)

If it were doing X internally it would be ten times as ghastly a program as it already is! :-)

Remote xbiff would be a solution, I suppose, but somehow I don't like the idea of having remote programs started automatically when my X session comes up. Local programs that attempt to make network connections, fine; actual remote programs make me nervous.