Postfix Security Hardening

[kextra1]

I'm running the lastest ISPConfig Stable 2.2.29

Debian
Postfix
Roundcube
Courier-*

I've also got additional programs such as:

postfix-policyd
smtpguard
postfix-smtpguard

My problem is that mail sent from my mailserver is showing up in the spam folder when a message is sent to an email address from yahoo, gmail, sbcglobal.net, and not even getting through to hotmail addresses unless they send me a message first.

So if a user signs up with an address like user@yahoo.com their account info is in the spam folder.

I've found a few links to get my server off of any list that blocks it for a few of these. The question remains....is there anything more that I can do to make sure my mailserver is secure and my mail gets through to the customer?

Thanks for any Tips, tricks or mod's that you fellas might be able to suggest.

[falko]

Please make sure you have a proper PTR record for your server and SPF records for all your email domains.