My non-profit association has an Exchange server and a ListManager server to handle announcements to our members (about 800 email addresses) and several low-traffic discussion listservs.
On the incoming side, we run Postini to filter all incoming spam, with some Spamassassin locally to catch the rest that Postini misses.
There is an issue where some of the mails we send out via our ListManager install are being flagged as spam in Postini, whereas some others get through. There doesn't appear to be a rhyme nor reason to which one it blocks and which it allows through. My guess is that we are right on the "threshold" of spam and some terms we use in the emails push it over the edge. 99% of emails are accepted by the server, but I suspect some services are silently throwing the messages out or placing them in spam folders.
So my question is: What are some guidelines to getting the best deliverability of these messages?
Some facts about our particular setup:
- We have 2 internal servers (one Exchange, one Listmanager), however both send email out using the same IP address.
- The MX record for incoming mail at our domain, and what most messages are sent out as (via email@example.com), is mx.mydomain.org. This is set up as the PTR entry for our IP address.
- Our ListManager is set up to use firstname.lastname@example.org as the from address, however it uses Return-Path: email@example.com to track bounce messages.
We have SPF set up for our main domain:
v=spf1 ip4:72.X.X.234/30 a:lists.mydomain.org mx:mydomain.org mx:lists.mydomain.org ?all
We are on the five-ten spam blacklist, I think they have us blocked because we are on Verizon with a static IP, and some folks block all of VZ.
Is there anything I am missing that should be set up to maximize the deliverability of our messages? Can we work with any of the big "whitelists" to help with this? What do the "big" mailers use? I have some thoughts but wanted to check with the experts here.
Thank you in advance for your responses!