FreeBSD Upgrade on production server

[Peter Rosa]

Hello everybody,

I wish to upgrade my production firewall / mailserver / DNS server from 4.3
to 4.8.
The simplest way seems to be use of CVSUP. OK, but...

Is it safe ? What should I backup ? There is running well-configured
sendmail - are
there some changes in its configuration between versions 8.11.3 used in
FreeBSD
4.3 and 8.12.8p1 used in FreeBSD 4.8.
This is my only mailserver and I don't have an secondary if something
fails...

Please, advice if you have some know-how :-)))

Peter Rosa