Hello aspangilinan,
@ Christian;
You looked at the wrong server... His hostname is zentyal.nsb.local and not the one that you looked at.Back to the point;
1) SMTP banner (zentyal.nsb.local) doesn't match the PTR (very bad)
2) SPF is missing (minor)
3) Your IP is currently listed @ APEWS since 2008-04-27 (minor)
Also, I would strongly suggest you to install "DenyHosts" since your SSH port is open
So, what you can do about it (
we all love solutions);
1) Change your hostname for the same thing that your PTR is showing
2) Create a SPF entry allowing your IP to send email from your domain
3) Visit APEWS and get unlisted (you may also contact your ISP for that matter)
APEWS website:
http://www.apews.org/** Just doing the first point should fix most of your delivery issues.
Best,
Marcus