Improve your deliverability in 3 steps

People getting started with improving their deliverability (usually right after discovering they have a deliverability problem), are often confused where to start. To help you get started, we give you three easy steps which will improve your deliverability.

  1. Configure Reverse DNS for your mail servers
  2. Create SPF and Sender ID records for your mail servers
  3. Process bounces religiously. Never mail real bounces again.

So, how do you do this? We'll try to explain.

Configuring Reverse DNS

Reverse DNS really isn't as hard as it sounds. Every mailserver you use has a hostname, for example: This hostname points to an IP address. A similar thing in the real world: your name in the phonebook points to your phone number.
So, what's Reverse DNS? It's the Caller ID of DNS. Imagine you get a phone call from a number, and the person says he's your friend Paul, but your phone doesn't display the name Paul. Would you think you might be tricked? The same thing happens with Reverse DNS.
The receiving computer takes your IP address, and looks up what it's primary hostname is. If this hostname differs from the one your server has, you lose trust. Less trust = less deliverability.
So, what can you do? First off, make sure you use machines dedicated to you for mailing. Second, contact your provider, and asks them to configure the Reverse DNS correctly. That's it. If you're not sure your Reverse DNS is configured correctly, consider getting a (free) report from us, we test this for you.

Creating SPF and Sender-ID records

Sender ID and SPF are mechanisms for proving that your mailserver is allowed to send e-mail for your domain. In the real world, you might get the Power of Attorney for your mother/father, well, this is the same, but for a domain.
When your mailserver connects to another server, saying it has a mail from, the other server might check this. The server fetches the SPF/Sender-ID record for, and checks whether the IP address of your server is listed as allowed. If it's not, you lose trust. If it is, you gain trust.
So, what to do here? Well, there are excellent SPF Wizards online to set up your records. Try these:
Open SPF wizard
Microsoft SPF Wizard

Important SPF/Sender-ID can be dangerous. For example: if you forget to list a server, it will hurt your deliverability. So, check with your sysadmins to make sure you get them all!. When you're done, you can always test a mail from all your servers with us, and we'll give you a free report.

Processing bounces religiously

A bounce is what happens when you send an e-mail to an address which no longer exists. You will receive the e-mail back (it bounces). Nice people register these bounces, and don't try to e-mail those addresses again, so the receiving server doesn't have to unneccessary work. Spammers however, don't care, and happily keep mailing to those addresses. So, at one point, the people who program mail servers decided that if you're generating too many bounces (more than 5% for example), you're probably a spammer, and they'll no longer accept mail from you.

So, what can you do? Well, you need to process your bounces, and never mail them again. However, this is quite hard, since bounce messages are not uniform (mailservers come in many languages and versions). There is one great trick your programmers can use. If you set the Return-Path of your e-mail to an dynamic address which will allow you to identify the person who bounced, you can unsubscribe them quickly. Be sure to check for a 55X or 5.5.X code in the mail, because it might be a temporary failure.

About is a online deliverability testing and monitoring service. We test all key deliverability points for you, and provide you with a report on your score. We offer free and premium tests, so you can check out what you'll get.