Postmaster - General question and DMARC reports

I’m pretty much fully up and running with my V2 (except for some calendar import issues), but overall I’m very happy, and tech support, including not only Phil but even from Giri and Dirk, has been absolutely terrific. Thanks all. Here’s a couple of questions that might be of more general interest and that the community might be able to help with:

So, I’ve got my Helm set up with secondary domains, and I’m receiving mail for addresses in those domains. But, I never actually set up any of the users to get mail on the primary domain. That seems to be working fine. However, I noticed that there appears to be a working “postmaster@primary-domain” email address on the Helm; if you send email to it, it doesn’t bounce, unlike other non-existent addresses. Is email to that address just collecting on the server? Do I need to create a user account for postmaster in order to go read them? Or is the email just going into a black hole?

I noticed the postmaster email address existed in the course of setting up the secondary domains: When you create a secondary domain, you have to set up the DMARC DNS records for the domain, and in there you provide a place for DMARC spam reports to be sent, which is normally “postmaster@domain”. So I set up postmaster accounts for my secondary domains as per the instructions. However, now that I’m getting those reports, I don’t know exactly what I’m supposed to do with them. They basically tell you if lots of spam is being sent using your domain name, but so far that information doesn’t seem terribly important. (The stats aren’t huge.) So this leads to my second question:

Is Helm (the company, not my box) doing anything with DMARC reports sent to postmaster@primary-domain, or (as I asked above) is that email just collecting in the postmaster mailbox, or going into a black hole? If they are collecting those reports and doing something with them, should I be forwarding the ones from my secondary domains to the primary domain postmaster instead? If they’re sitting on my Helm, is there anything useful I can do with these? Or should I just turn off DMARC reporting?