IP address and sender reputation

As a marketing professional and a frequent sender of email marketing messages you have most likely heard about reputation and IP addresses. A good reputation will help your communication and a bad reputation is harmful. In this article we explain just what this really means and how it relates to the IP address you send from.

What is IP reputation?

Your reputation refers to the reputation of the IP address you are sending emails from. It's a scoring model that signals to ISPs* whether you should be considered to be a good sender, a not so good sender or even a spammer. Every email campaign you send out will influence your IP address reputation.


*ISP = Internet Service Provider or Inbox Service Provider. In this case, we use ISP as a collective term for the companies providing the email services e.g., Gmail Outlook Live and Yahoo.


Boosting reputation  Lowering reputation
Good recipient activity with high- and consistent open rates Poor recipient activity with low- or decreasing open rates
Low complaint rates High complaint rates
Low number of unknown addresses and bounces High bounce rates, unknown addresses, hitting spam traps
Structured sendout pattern and strategy Occasional ad hoc sendouts now and then with low engagement 

What is an IP address?

In simple terms, an IP address a "location" from which you as a sender communicate with your receivers (customers) via the Internet. All emails are sent from an IP address, and you can either have your own dedicated IP address, a shared IP address or send from an IP pool.

Dedicated IP address: Only one sender is sending from the IP address.
Shared IP address: Several senders are sending from one shared IP address.
IP Pool: Several senders are sending from a certain amount of IP addresses.

There are some different aspects to look at to understand which option is the best for you. The two main aspects are volume (how many recipients you send emails to) and frequency (how often send-outs are made). An IP address needs to be kept warm and this is done by sending emails regularly to a good volume.

Senders with larger volumes (around 1,000 000+ emails per month) can use a dedicated IP address while senders with smaller volumes can benefit from using a shared IP address or a IP pool. Here are some pros and cons with each solution.

Sending from a dedicated IP address

Pros Cons
Only you oversee your IP reputation, no outside factor can affect it. It's all up to you to keep up the reputation of the IP address.
ISPs generally set limitations to how many emails they can receive per minute from an IP address—you do not have to share this rate with others. If you're sending too few emails, the IP address runs the risks of getting cold which is bad for your reputation.
Possibilities for allowlisting programs for certain domains.  
Better control over your deliverability as you are the only one affecting it.  

Sending from a shared IP or IP pool

Pros Cons
Good for low-volume senders because the IP-address(es) are always warm. You as a sender don't have full control of the reputation.
Multiple good senders are helping each other to keep the IP reputation up. You must share the traffic with others and when there is a lot of traffic, deliveries to certain domains can be slower.
  Continuously poor sendings from other senders can end up effecting the reputation for the IP address(es).

There will always be pros and cons with respective approach and the setup models mentioned in this article covers different solutions suitable for different kind of businesses. Our Deliverability Team will always make sure that your setup is optimal for your specific needs.

What about domain reputation?

In this article we've mostly explained how your IP reputation can be affected by your actions. Another key player in this game is something called domain reputation. The ISPs* are getting better and better at separating the IP address reputation from the sender itself (the sending domain). So, if you are sending from a shared IP address or an IP pool, it's good to know that there are other factors besides the IP address reputation that are in play. The "Boosting and Lowering" table above applies in the same way for domains reputation though.


Good user engagement, a proper email send-out strategy, and good list management will help boost your reputation as a sender.

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