A question about spam?

Hi everyone,
I have a question about spam filtering.
Now before you work from the idea that I am running Linux directly, I am 
not.  Instead  I am a member of a service that uses Ubuntu 16.04 in a 
shell capacitor.
Since we changed over to Ubuntu, I find the spam is profoundly greater.
Granted, a couple of recent hacks of major services might be impacting 
things as well.
I should ask other members of shellworld what their lives are like spam 
wise.

My question for you though is this.
We have Spam assassin here, and I do run sa-learn.
However, I do not run this on addresses that use real names, even if I 
know the material is spam.
At what level do programs like spam assassin do the filtering?  Are there 
other steps I can take to curb the flow?

Thanks,
Karen