(21-07-2017, 03:22 AM)z3bra Wrote: I'll setup DKIM/DMARC then, as it's the last point I can improve.

Domain keys identified mail is one of the most important part of the mail infrastructure these days. It assures that mails are sent from the right server and can be traced back to an authority.
As far as I know Microsoft mail servers (hotmail, live, etc..), won't accept any email, complete nuke them, if they aren't signed by the mail provider.
Gmail is a bit more loose and will mark it as spam.

Here's a good guide to set it up:
https://www.digitalocean.com/community/t...ian-wheezy