smail/exim/qmail/zmailer/... which MTA?

[Michael Laing <mpl@ucook.com>]

Can someone make a recommendation to me of which to use?

I am going to be handling email for 30-100 busy users.

There are 3 domains, but only one user list, i.e. mbar@foo.com is the
same as mbar@fi.com.

I am using smail right now and a text '/etc/aliases' file, generally
there is one alias per user - seems a little clunky to administer.

In the near future I may need to handle daily bulkmail to a list of
users in the 20,000-100,000 range.

Thanks,
Michael