On Tue, Feb 16, 2021 at 11:03:14AM -0500, Dan Ritter wrote: > Stefan Monnier wrote: > > Still, there is to me no good reason not to allow installing both exim > > and postfix at the same time. I think it's just a tradeoff between how > > often this could be useful and how much work it takes to tweak the > > packages. > > An MTA has to provide certain things, or else it is not an MTA. > > One of those is a daemon listening on port 25. > > Another is a /usr/sbin/sendmail command that accepts new mail. > > There is no requirement that the sendmail command use > localhost:25 to get the mail in; it's perfectly acceptable for > it to: > > 1. Do all the work itself, or > 2. Use a socket to hand it off to the rest of the MTA, or > 3. Send it off to another machine somewhere, even if it's > destiny is to come back to this box > > among other things. > > So one package has to control both the port 25 daemon and the > sendmail command. > > Debian policy is that, whenever possible, a package providing a > daemon should start that daemon at install time. This is, > perhaps, one of the more controversial policies, but it is in > effect and has been for many years. > > Therefore, installing an MTA will get you both a port 25 daemon > and a sendmail command, and remove any previous installed > services. > > If you keep the config directories in place, you can switch > between MTAs and feel reasonably confident that when you do > that, via apt install, it will be started with the configuration > that you already set up for it last time round. The exception > are some shared files like /etc/aliases, where you should not > expect a restored MTA to restore that config as well. Hence my > suggestion of etckeeper. > > If one is trying to learn different MTAs, a few days or weeks > with each is not out of the question, and the 10-45 seconds of > apt install to change between them is reasonable.
Talking about learning multiple MTAs - using a virtualization environment + configuration management (ansible/chef) + apt-cache-ng works excellently. I have been using VirtualBox VMs (under Win10) with NAT network and ansible + subversion to learn and get dma, exim, opensmtpd as well as postfix to work for my production requirement. My probably inconsequential contribution to this discussion. Didar > > -dsr- > -- Them as has, gets.
