The DNS configuration will get your server flagged as a spam engine.
$ dig +short MX bwnetwork.net
0 bwnetwork.net.
$ dig +short bwnetwork.net
92.236.101.231
$ dig +short -x 92.236.101.231
cpc3-stav18-2-0-cust486.17-3.cable.virginm.net.
$
The forward (name to address) and reverse (address to name) translations should match. I also can't tell if you're on a dynamic IP or not, but that'll be a problem if you are. You'll want static IP. Also with your ISP, you'll want the reverse translation of your IP address configured to bwnetwork.net,
If you can't get onto static IP or if your ISP won't set up reverse DNS for you, then you'll likely need to move to a mail relay service.
Your IP is also included in the Policy Block List at Spamhaus, which implies that you're going to have serious problems getting mail to work; this usually means your IP address is in a dynamic IP address block and your ISP has added the dynamic block to the blacklists.
There is nothing you can do on your server to fix these problems, either. What I've listed here is within the public DNS configuration, and within the local ISP configuration, and with how other mail servers will determine whether or not your mail server is legitimate or is flagged as a spam engine. Mismatched DNS gets you flagged as a spam engine. Given the policy black list entry in use here, I also wouldn't be surprised to see the IP address have a TCP port 25 block within the ISP network, too.