Sorry for yet more noise, but downgrading to exim_3.03-5_i386.deb fixed the problem. I still think it has something to do with the fragmenting as suggested by Wouter, because when I do a traceroute -F smtp.student.unsw.edu.au, the last hop fails with
[snip] 129.654 ms !A * 119.699 ms !A I'll have to find out through the exim people. Thanks, Mark.
