IP addresses and deliverability

As recently as a couple of years ago, deliverability was all about content. People obsessed fervently over spam checks, tweaking every word to reassure spam filters of authenticity.

But these days, it’s a whole different story. With an estimated 80/20 balance between IP reputation/ domain authentication and content, it pays to be aware of both aspects.

Return path’s deliverability report shows that about 10- 20% of emails will get junked or lost in cyberspace due to spam filters, a frightening statistic for any marketer.

Luckily, it appears Europe isn’t doing too badly with nearly 90% of emails making it through to the inbox. By contrast, North America lag behind on 80.1% which, while not disastrous, means they could be learning a thing or two from their friends across the pond.

Non-Delivery Rates by ISP

So how can marketers increase deliverability? The first step is to take responsibility for your output. We can broadly separate the issue into four areas: authentication, reputation, content filtering and IP addresses.


Authentication is an ISP-based process designed to verify the domain name of any emails they receive. As you might imagine, this makes it the first line of defence. It’s designed to prevent phishing attacks where someone sends you an email masquerading as someone else.  The reputation of your from address and from name may become more important in the future, expect more from us on that another time

IP Reputation

When it comes to email marketing, reputation revolves around a few key features:

  • Blacklisting – ensuring your domain hasn’t been added to a black-list
  • Volume/ rate – ensuring you don’t send too much email
  • User-voting – whether recipients have marked your message as spam
  • Bounce management – ensuring you remove email addresses that have hard bounced
  • Behaviour – complicated algorithms attempt to spot spammers based on sending habits.

Content Filtering

In modern times, this has become the real point where spam lives or dies. Systems now consider images, the body of an email, how it has been constructed, the subject line and the links. As technology becomes more sophisticated, detecting content which doesn’t pass the grade has moved forward in the same way; just look at your junk folder for proof of this.

And then there’s the matter of IPs…

How does life affect my IP at dotMailer?

Many clients decide to share their IP address with several others. We have a number of ‘pools’ of these senders, all sharing a level of behaviour and reputation of their neighbours. If your emails are judged to be ‘behaving well’, you could be promoted into better and better pools to ensure that emails of a similarly reliable standard don’t risk having their reputation ruined by an errant newcomer.

This works especially well for those clients who are not sending in high enough volumes or regular enough frequency to maintain a high IP reputation by themselves on a dedicated IP (more on those later.)1566-553416

This also means those trying to send using poor quality data, which attracts complaints and bounces, can’t bring down those who really strive to keep their standards impeccable. The only way these senders will reach our superior pools is by changing their behaviour and increasing the quality of their data.

Dedicated IPs

But there is another option. Some of our clients send enough emails and to such a high volume of qualified recipients that the best route for them is to have their own IP dedicated to such traffic. This eliminates the risk of anyone else having influence on your IP reputation or deliverability too.

As we are continually warming new and fresh IPs (as a member of Ripe) through our series of pools we give all clients who want their own IP a pre-warmed IP with a fantastic reputation.


One of the additional benefits of having your own IP is that you are then make use of the certified  services offered by the companies like Goodmail or SenderScore. These companies will monitor your IPs to see if you meet the acquired standards for certification.

The big upside for certified senders is that they guarantee emails be to be delivered to the inbox with links and images enabled on certain ISPs. Have a look at the Goodmail and ReturnPath to see who they work with in more detail.

Some say that if you have clean data and good practices you don’t need to be certified to get delivered to the inbox, which is true. However it offers an ‘insurance policy’ for those really important emails and we see many clients use this for transactional emails. Furthermore, you can be more visually adventurous with your emails and go to town with the creative. You can do this in dotMailer using our easy to use segmentation queries.

The moral of the story is that you need to nurture your IP address. If looked after, it’s a resource that will serve you for as long as you need it to and never let you down. We at dotMailer can offer you a variety of different solutions depending on your requirements and sending patterns.