[systemd-devel] Alais for SMTP providers

[Kenneth Porter]

I just finished adding a custom service to send an email on system 
shutdown/startup, based on this article:

<https://askubuntu.com/questions/851946/send-me-an-email-on-computer-shutdown>

I ended up coding an After for postfix.service so the mail would get get 
delivered before the system shut down. I'd like to be able to use the same 
unit file on older systems that use sendmail, and I know there are other 
packages that provide SMTP and local mail. So it would be desirable to have 
an Alias for those services. I'm using CentOS 8 (7 on older systems). Is 
this perhaps already present in a newer commit? Is there a registry for 
well-known aliases for package writers?