I have used Zimbra for quite sometime but am running into a few issues that I would like a professional to take a look at.

Currently Running with Split DNS
Zimbra 7.2.1_GA_2790
Centos 5.8 x64

I have 4 domains which send through this server and I need to:

properly setup DKIM
make sure spf records are correct and audit DNS records.
make sure headers are sent with correct info

Although these issues should not be complicated I have been having a rough time getting them 100% correct which in result has gotten many of our emails sent to junk folders.

I would like a pro to check through the setup of the server make any recommendations necessary.