As we mentioned in the previous post, the source of an e-mail is one of the important criteria that ISPs look at in the first place. The two elements determining the resource are the IP address and the domain.


IP address


It is a series of numbers that send to your domain name and are included in the domain names system. On the other hand, ISPs decide whether the transmitted content belongs to the inbox or spam folder by looking at the reputation of this IP address that sends on your behalf. There are 2 types of IP addresses:


Dedicated IP: Using only one company and sender.


Shared IP: Can be used by many companies and senders at the same time. Since the general reputation depends on all emails that come out over this IP, it cannot be controlled by a single sender. Even if all senders using IP follow the correct rules, spam-sending by a single user will negatively affect the deliverability of all other senders.


Importance of consistency


Delivery consistency depends on the email history on your IP address. Many marketers send to their entire list over the new IP without knowing the results at the very beginning of the email marketing kick-off. Whereas, ISPs generally place them in the spam folder by applying restrictions to the e-mails sent over the new IP until the sending volume and frequency meet a standard. After a certain order is achieved, the restriction is reduced or removed completely.


The reason why ISPs apply such a restriction is that they are generally malicious, spammers always want to lose their tracks by switching to the new IP. Therefore, sending in stable volumes over a single IP for a certain period of time will bring you to the position of an authorized sender and allow you to enter your inbox.


Speaking of consistency…


Don’t run away from issues: You can’t escape by switching from one low reputation IP to another. You will provide a more permanent solution by correcting the mistakes made, otherwise, you will continue to have the same problem in the IP you will switch to.


Don’t switch from one IP address to another: It’s not always advantageous to send over many IPs. Since spammers trying to mislead the system generally try to gain an advantage by using more than one IP, a single IP should be preferred as much as possible.


Heat your IPs: In order for your new IP to have a good reputation, you need to heat it with a small number of regular submissions.


Send in a consistent volume: ISPs closely monitor inconsistent, very few, and very high volume sendings. It is highly important that you send consistent volumes even after the reputation of the IP you have is settled.




A domain name is a name in which your name is registered in the internet world (eg Domain reputation is the reputation of this name from which e-mails are sent. The domain address is owned by the sender itself, thanks to the DKIM settings.


Some criteria that play an important role in determining domain reputation are as follows:


  • Spam Placement Rate: The number of times email sent from a domain entered the spam folder, depending on IP reputation or inward.
  • Inbox Placement Rate: The number of times e-mail sent from this domain entered the inbox
  • Complaint Rate: How many times e-mails sent from a domain are marked as spam
  • “Not spam” Rate: The number of times e-mail sent from a domain and falling into a spam folder has been marked as “not spam”

We will talk about list quality and subscriber complaints in our next post.


Previously on this guide:

The Essential Email Deliverability Guide Part 1 – Know More About Spam And Spam Filters
The Essential Email Deliverability Guide Part 2 – Spam Filter Types and Filtering Methodology