On doing an upgrade install, using sysinst, sendmail gets removed but
/etc/mailer.conf does not get updated, resulting in lots of garbage
error messages because soemthing cannot find sendmail.

This is bad.

There are two options:
1) update mailer.conf to point to the appropriate places for postfix
2) do not remove sendmail

In this particular case, I have not done any customisation of sendmail
or mailer.conf so it should be reasonable for (1) to have been done.

However, if I had of been using sendmail and updating the binaries in
various places then I would be now quite upset that the had been removed
and in whch case (2) would be the answer.

Darren