Guidelines for Mail Servers - How to Maximize Deliverability to Remote Inboxes

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 protected]), is mx.mydomain.org. This is set up as the PTR entry for our IP address.
• Our ListManager is set up to use [email protected] as the from address, however it uses Return-Path: [email protected] 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!

Solution 1:

I'm not sure if you're sending bulk email or running a discussion group. Most of my advice is for bulk email sending..

Email delivery is 30% configuration and 70% list management.

Configuration:

• Use SPF/DKIM/Goodmail (if applicable)/etc
• Make sure your reverse DNS is set up properly
• Use the same IP addresses consistently
• Use the same from addresses consistently

List management is far more tricky:

You need to remove old addresses from your list. This can be incredibly difficult for marketing people to wrap their heads around, but it's the single most important thing you can do. Far more important that message content, SPF, etc etc. Well, maybe not reverse DNS that's the single most important part.

Specifically for list management:

• Get on the hotmail/AOL/Yahoo/etc feedback loops. They send you the people who mark your emails as spam so you can remove them from your list.
• Remove bouncing email addresses
• Track user open/clickthroughs for each user. If a user hasn't opened/clicked through an email in in 60-90 days, remove them from your list.
  • I've segregated 'old' email addresses onto different IP addresses in the past to avoid polluting the 'A' list in the past.
  • Hotmail (and possibly others) take old and unused email addresses and turn them into spam traps. Sending email to these repeatedly is an extremely bad idea.
• Establish solid relationships with the domains you send the most email to, or the spam lists that you end up on the most. If you work with them and follow best signup/unsubscribe practices, they're usually quite helpful.
• Get your users to add your from address to their address book. A lot of email carriers use this as a white list (hotmail, gmail, etc)
• Do everything you can to get off of blacklists. You're on them for a reason. Fix that reason and most of your problems will go away.

I'd say 9 times out of 10, you're better off to outsource your email sending to someone else. It's a huge job to manage this process for any decently sized list.

Solution 2:

I posted the following answer on this thread.

You'll probably want to look into DKIM as well: http://www.dkim.org/

Yesmail is a mail marketing company that takes care of a lot of these issues.

Other things that you can do are

• Run your emails through Spamassassin before sending them, to make sure they don't score too high.

• Avoid HTML

• Avoid URLs

• Make sure your users know to add your outbound email address to the address book or whitelist, and then stick with that address.

• Related to the above, try to have just one outbound email address that the messages come from.

• Make sure your mailserver's IP address resolves back to the domain name it claims when talking to other mail servers.

• Use TLS if possible.

All of the above are basically things that spam filters look for when evaluating a message, so your ultimate goal is to avoid as many triggers as possible.