Bug#770281: dh-systemd: dh_systemd_enable --no-enable not working as expected

[David Lechner]

As you wrote, systemclt status says:

 >    Loaded: loaded (/lib/systemd/system/spamassassin.service; disabled)

So, the service is "disabled" as expected. I think what you want in 
addition to "dh_systemd_enable --no-enable" is "dh_systemd_start 
--no-start" so that the service does not start when it is installed.