[Pkg-systemd-maintainers] Meta dependencies in unit files?

[Moritz Muehlenhoff]

Hi,
I've been studying some unit files and I stumbled upon Fedora's service file
for clamav-milter: 
http://pkgs.fedoraproject.org/cgit/clamav.git/tree/clamav-milter.systemd

I contains the following snipped in the [Unit] section:

| Before = sendmail.service
| Before = postfix.service

Is there the equivalent of Debian's "Provides: mail-transport-agent" for unit 
files? The above wouldn't really scale for Debian if the respective unit file 
needs to be updated whenever another MTA ships a systemd unit file?

Cheers,
        Moritz