Email Deliverability

Warming up IP addresses

Whether email marketing is a brand new thing or you’re a seasoned veteran, you’ll most likely have come across the idea of “warming” IP addresses.

Questions about warming IP addresses come up a lot and our answer is always the same. There’s no silver bullet for doing it right although the principles and objectives remain the same.

Why do we warm IPs?

ISPs use the sending IP address as one of the pieces of information that helps to determine sender reputation. A brand new or cold IP has no sending history and therefore ISPs don’t have anything to go on.

Think of IP addresses as a way of providing ID to the mail servers you’re sending emails to.

If your IP has little history or there’s some black marks from the past then it will lead to slow delivery, bounced emails and possibly even blocks. Run your sending IP addresses through and to get the complete picture.

Warm-up basics

Here’s a few things to remember when warming IP addresses:

  • Even red hot IP addresses won’t get you past bad practices
  • Regular volume is needed
  • Pre-warming doesn’t really work
  • Stop sending email from an IP and it’ll go cold
  • IP reputation is not permanent
  • Warmed IPs can be affected positively and negatively if you change the type of email sent using it

Does the sending domain matter?

The sending domain plays a big part and you’re obviously going to want to ensure Email Authentication is correctly configured to ensure emails aren’t rejected or filtered.

One more thing to consider is the age of the domain. Brand new domains are sometimes referred to as “Day old bread” and some mail filters will reject emails sent from a domain classified as that.

A brand new IP and domain combo isn’t going to produce good results so get things setup in advance.

Step by step

Warming is a gradual process so take your time. Go too fast and you’ll be taking big backward steps but when done in the right way you can achieve results in a pretty timely fashion all things considered.

Here’s a few pointers:

  • Throttle delivery speed initially to one thousand or less emails per hour
  • Email users that will engage with your emails before sending to inactive users
  • Send regularly and consistently
  • Check hard & soft bounced reports after each send
  • Increase email delivery speed slowly

If you’ve not come across the idea of warming before it’s probably because the ESPs you’ve used in the past don’t offer dedicated IP address options. Those guys group senders into pools of shared IP addresses and warming is all taken care of.

For anyone that uses dedicated IP addresses this is a very important part of email marketing and more specifically, sender reputation.

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