In the ideal e-marketing world, your member lists should consist of people who are actively interacting with the content you send and who want to receive messages from your brand. Creating the list quality in line with your targets will provide a very high benefit in deliverability.


ISPs track the e-mail inboxes you send to and if you have a bad list structure, they can filter your content or block it completely. There are 3 different types of users followed: Unknown addresses (invalid), “spam trap” addresses, and inactive users. User spam complaints are also critical for signifying bad list quality and are of high importance in the filtering phase.


Unknown users


Unknown users are addresses that have never existed or their membership has been terminated by the ISP or has been abandoned by the user. Another known name is “hard bounce”. Since the message sent cannot reach the person, 550 error codes are reported by ISPs. Such addresses should be removed from your list immediately. The unknown user rate is obtained by the ratio of the number of unknown users to the total number of users sent. To enter the inbox with high rates, this figure should be below 2%. The unknown user rate exceeding 10% will cause you to have serious problems in deliverability.


Spam Trap addresses


“Spam Trap” addresses are e-mail addresses that do not belong to any real person or institution and are created purely for feed purposes. Since they do not have the ability to be opt-in, the way they enter your data list is either against the rules and permissions or is poor list hygiene. Mailing to one of these addresses will result in surveillance of your IP, in good probability, and in the worst case, blacklist.


There are two types of spam trap addresses:


Reactivated spam trap addresses: Even if your entire data list is made up of members with permission, some addresses may be “Spam Trap”. The main reason for this is that ISPs convert addresses that have not been used for a long time to “Spam Trap” addresses. The goal is to encourage email marketing to always be done to an active audience.


Addresses created to catch spammers: They are usually embedded in e-mail lists for sale or intentionally embedded in websites to be found by robots.


Here are some suggestions for clearing invalid and spam trap addresses:


  • Quarantine new data: Keep your new data list separate until you send a welcome email and receive “invalid” confirmation.
  • Increase the easiness of information updates: Users can frequently change their e-mail addresses. Easy change of membership information will reduce the number of invalid e-mails.
  • Use double opt-in permission structure: The address whose membership is confirmed by a second e-mail sent will definitely be a valid address.
  • Choose the data source carefully: Check the data you will obtain from third parties periodically and inquire where it is obtained from.
  • Email your subscribers regularly: In general, sending less can cause you to encounter a high volume of invalid addresses. Frequent sending will increase awareness as addresses that have not been used for a long time are converted to spam trap addresses.
  • Check member activities regularly: As a general rule, the user who has not interacted with your content for nearly 1 year is no longer an efficient member for you and should be removed from your list immediately.
  • Perform a simple list cleanup operation: You should clear generic addresses like, unusable addresses like, or addresses with obvious typos like @ from your list.


Passive addresses


Passive addresses, in short, are people who are on your member list but do not read, click or take any action.


Passive members can cause many unwanted consequences. It can be an invalid or spam trap source, as well as negatively affecting your reports and reducing your overall reputation.


The measures to be taken are very simple:


  • Identify passive members.
  • Actively monitor read, click, and ‘bounce’ figures. Whenever the numbers begin to fall, do the necessary cleaning by comparing it with the original level.
  • Try to identify the data source of passive addresses. Whichever channel or platform it comes from, it will be easier to take action.


Spam Complaints


The primary purpose of ISPs is to protect their users. For this reason, they attach great importance to their feedback and preferences. If the recipient complains (marks spam) about the e-mail sent, the ISP will consider the e-mail unsolicited and block future submissions. As a result, complaints are one of the most important criteria for a low reputation.


There are 3 ways users can file a complaint:


  1. Spam button: It occurs when the user presses the spam button.
  2. Postmaster complaint: It occurs when the ISP sends a complaint message to the “postmaster” address.
  3. Filter application complaint: The user applies to the filtering application or to the blacklists that accept the user complaint.


Users can complain for many reasons, trying to find the source of the problem will at least reduce the problems. Our recommendations in this direction are as follows:


  • Identify possible complaints by examining the source of the member lists. Or do not use data when you are not sure about the source.
  • If the member does not remember your brand or why they were registered on your list, they will most likely complain to you. A “Welcome” e-mail sent with the right content at the right time will strengthen your interaction by telling your member how often you will reach out with what kind of content.
  • Content that does not interest your member will receive a high rate of complaints. Learning the preferences of the members and presenting content in this direction will enable you to make targeted marketing and reduce the number of complaints.
  • Make sure that the unsubscribe link is easily accessible. The user who cannot find the exit link will press the spam button without thinking.
  • With the “Feedback loop” program, immediately process the complaint lists submitted by ISPs and remove the people who do not want to receive e-mail from you.

Remember, even the tiniest rate of complaints can have a huge impact on your inbox access rate. Generally, the spam complaint rate should not exceed one in a thousand (0.1%).


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

The Essential Email Deliverability Guide Part 3 – The Impact of IP Addresses and Domains