[CentOS] Mail server with both postfix and sendmail installed, active MTA gets switched.

Sat Jan 5 07:18:57 UTC 2019
Gordon Messmer <gordon.messmer at gmail.com>

On 1/4/19 8:29 PM, Lamar Owen wrote:
> I have had updates twice now switch the active MTA to sendmail, and I 
> have to manually 'systemctl disable sendmail; systemctl stop sendmail' 
> and 'systemctl enable postfix;systemctl start postfix' afterwards.

Run "systemctl mask sendmail" as well.  That should permanently disable 
the service.

> I am trying to find out what package update caused this to switch; or 
> which logfile to look at to show me the systemctl messages that show 
> the enable/disable sequence and points me to the correct package to 
> file the bug against.

You could look for any package that refers to sendmail in a script or 

rpm -qa | while read pkg
   rpm -q --scripts --triggers "$pkg" | grep -q sendmail && echo "$pkg"

> Sendmail hasn't had updated packages in a long time, since August 
> 2017. None of the package scriptlets from the above packages look like 
> they would affect the sendmail setup.  So, I'm looking for suggestions 
> on where to start looking for the data to ferret this out; no clues 
> are in /var/log/messages or /var/log/yum.log. 

If the problem is a trigger on the sendmail package, it could run 
without any changes to the sendmail package itself.