In response to Suresh Ramasubramanian:
> > rm -f /var/spool/exim/retry*
> Wouldn't fgrepping for whatever mail is stuck (maybe by message id, domain et
> c)
> and deleting only that file help?
No, there is not a file for each message, only a single database with
one or more files (depending on which DBM you are using) and a
lock-file (all usually in /var/spool/exim/db, depending on your
compile-time options and configuration).
Personally I do use exim_fixdb; an interface to that in eximon might
be nice but I manage fairly well without it. Or, if I am sure that
the machine at the other end is back up, exim -qff.
Gyan.