Trouble-free steps to upgrade mailscanner?

[Dan Stromberg]

Hi folks.

(If we can work out a really good, no-hiccup procedure, I promise to
give back by writing up the process for a web article - I'm a bit of an
obsessive note taker/summarizer.  That is, assuming someone hasn't already
done so :)

I have a busy mail server running MailScanner 4.36.4, part NFS, part local.

I need to upgrade it to 100% local MailScanner 4.53.8 (or maybe 4.53.6).

If this mail server goes kerflooie, it's not going to be pretty.  At all.

I'm assuming I'll need to work out the local vs NFS thing with
site-specifics of course, but what are the basic steps one needs to follow
to get a trial and tribulation-free mailscanner upgrade - getting it right
the first time?

For example, is there a way to have two versions of mailscanner running on
the host at the same time, so you can test the new one, and cut over later
once you feel confident about the new one by doing something simple, like
changing a symlink and restarting a daemon?

I'm guessing you'd probably need 2 distinct pairs of sendmail's, but what
else might one require?

Thanks!