Factors Impacting Your Email Sending Reputation

Internet Service Providers (ISP) process billions of emails every day and use artificial intelligence to help them decide what emails should be blocked, sent to spam, or added to the inbox. To effectively and efficiently do so, they assign a reputation score to each sender's IP address. Your score is based on the results from spam filters and your listing on a blacklist. Your score is continuously changing, and it is different for each ISP.

At the beginning of the day, you may be marked as SPAM by Gmail and allowed to an inbox by Office365, but then you may no longer be marked as SPAM by Gmail at the end of the day. To better understand what factors are incorporated into your reputation score, we will first describe what actions actual spammers take that ISPs are trying to block. Then we will outline what you need to do to maintain a great email sending reputation.

How Spammers Earn A Bad Reputation

Spammers typically purchase third party email lists or scrape email from the web. They stand-up an email server and send a few million emails, and then they are gone. After pausing for a few days, they will repeat the same pattern with a different domain and IP. These spammers typical send:

  1. Ads - Ads are probably the most common types of email spam. These emails promote products and services, such as weight loss pills and tennis offers. In many cases, the offers may be a scam, but they also can be legit.

  2. Chain Letters - These emails tell you an exciting and thrilling story that persuades you to pass the message along under penalty of having something happen to you. Be careful, or you're going to have a run of bad luck.

  3. Email Spoofing - These are related to phishing scams can be very costly to those who fall for them. Spammers or phishers impersonate someone or a company and try to fool you into giving them information such as your social security, credit card number, money, user name, password, etc.

  4. Hoaxes - In this case, spammers offer miracle promises, such as, for example, "get rich in less than a month" or "gain the body of your dream by eating more and working out less". Spammers capture your attention and direct you to a malicious website.

  5. Money Scams - All of us know someone that has received the promise from a Nigerian prince that if we send him a small amount of money, he will reward us in a big way. These lending schemes a small amount of money to get a big payday have cost victims an average $2,133. Other money scams include asking for money for hungry children in Africa or requesting money to help with a natural disaster.

  6. Malware Warnings - These types of email notify you that a virus or ransomware has infected your computer. For you to solve this problem, you need to provide some information or download an attachment. Do not do it; if you do, your computer will likely get hacked.

  7. Porn Spam - This is a widespread spam tactic to get people's interest to buy pornography and, even worse, blackmail individuals.

Some characteristics of spammers that affect their reputation include:

Inconsistent Volume - Unlike businesses, spammers do not ramp up their email over a while as their subscribers grow. They acquire lists and ramp up their email sends overnight. Because of inconsistencies in sending volumes, spammers get a lower sender score and domain reputation, which increases their likelihood of going to spam.

Blacklists - Spammers are well known for burning through multiple IP addresses as they get blacklisted. Over 300+ blacklists have been created to capture spammers. These blacklists are used by various ISP and filtering software. There are two main types of blacklists:

1. Domain Based - These blacklists look for domains in the email body that have been associated with spammers. These domains include initial email links and final redirect links. Some example of these blacklists include:

  • SpamHause DBL


2. IP Address Based - RBL and DNSBL are used to identify whether the IP of a sending server is an open relay or has been used by spammers or by an email service provider, allowing spammers to use their infrastructure. Some of the common IP based blacklists include:

  • Return Path Reputation Network Blacklist (RNBL)

  • SpamHaus Blacklist (SBL)

  • Exploits Blacklist (XBL)

  • Composite Blacklist (CBL)

  • SpamCop Blacklist (SCBL)

  • Passive SPAM Blacklist (PSBL)

Spammers constantly check if their sending IP is on any of these blacklists, and when the IP is burned, they switch to a new one.

SPAM Traps - Spammers encounter spam traps all the time. Because they are purchasing email lists and harvesting websites using crawling technology, they often pick up email addresses published to trap spammers. As the sender deliverability decreases for an IP address due to spam traps, the spammers will eliminate the IP and start fresh with another IP address. Services like Sender Score can help spammers know if they have encountered any SPAM traps.

Bounces - Spammers encounter many bounces from their email lists since they purchase or acquire lists that may have spam traps, outdated receivers, and wrong email addresses. Many bounces signal to the email service provider that the sender is possibly a spammer, and consequently, the sender's reputation score is lowered, or the sender is blocked altogether. Two specific types of bounces can occur when a subscriber cannot be reached:

  1. Hard Bounce - Hard bounces happen when an email is sent to an address that does not exist. Usually, hard bounces are caused by someone using a fake email or entered incorrectly. High bounce rates suggest senders either have purchased a list or practice bad email list hygiene. Many hard bounces strongly signal that the sender may be a potential spammer.

  2. Soft Bounce - These bounces have a much smaller impact on email delivery since a soft bounce signals a temporary failure in email delivery. Soft bounces happen because the recipient's email mailbox may be full, down, or out of the office. Re-trying sending a message may work, but the sender should remove the email address if the failure occurs several times.

SPAM Complaints - Spammers most likely will get many complaints from their email. All subscribers need to do is mark the email as SPAM, and the complaint is submitted to the ISP (Gmail, Yahoo, AOL, Outlook, etc.). SPAM complaints are taken very seriously since the receiver is manually entering the complaint. Even a small complaint percentage such as .3% will stop your emails from reaching your subscribers' inbox. Spammers do not take the time to apply good email list hygiene practices such as double opt-in, simple 1-click unsubscribe, and proper list segmentation that can prevent you from receiving complaints.

IP Reputation - Spammers try to work around SPAM filters by using new IPs and rotating them. Spammers are not looking to build a long term reputation, and spam filters know that. For ISPs to identify spammers, SPAM filters look for actions that signal IP addresses permanence. They look at mailing history, past behaviors, and current activities to decide the IP's reputation. Based on their assessment, they may throttle your sending until they feel you are a legitimate sender. Sending too many emails on day one will damage your reputation and will most likely not be allowed. IP's need to be warm up by slowly sending emails over time. Only when ISP see a consistent pattern in sending engaging emails will they lift any throttling restrictions. Your IP age plays a significant role in your sender's reputation.

Subscriber Engagement - Spammers have low subscriber engagement rates, and for mailbox providers such as Gmail, low subscriber engagement is a vital metric signaling SPAM. Suppose SPAM filters detect that subscribers are not opening their email, clicking on your emails, not adding you to your contact book, or moving emails from spam to an inbox. These actions signal to the SPAM filter that your audience does not find value in the message being shared, and over a period of time, the mailbox provider will start sending all sender's message straight into SPAM.

By learning how spammers act and how they are detected, we can know what not to do to keep an excellent email reputation. The next section will address the steps senders should take to build and maintain a strong email sending reputation.

How To Maintain An Excellent Sending Reputation

Maintaining an excellent sending reputation is similar to keeping a good credit score. It takes time to build up a good credit score, but you can also destroy it overnight with a few wrong choices. Those with good credit scores can borrow at a lower interest rate, and those with good sending reputations can get their emails delivered.

To build an excellent sending reputation; it starts with your IP address and domain. SPAM Filters and ISPs use your IP address and domain to determine your overall sender reputation. The better your domain reputation, the better deliverability and open/click-through rates you can expect, and the more emails you can send. If your domain gets burned, it will be practically impossible to fix its reputation.

Select The Best IP Strategy For Your Sending Volume

There are two types of IP addresses you can use to send emails.

  • Shared IP Address - On a shared IP pool, such as G Suite, Office 365, and other ISPs, you will have many companies sending from the same IP address. The benefit of a shared IP pool is that many companies sending emails will lead to a consistent email volume that will improve your email deliverability. If your email deliverability and open rates are below average, you will most likely get an uplift in deliverability. On the other hand, if your deliverability is better than the other companies, you will likely see a dip in deliverability. Additionally, if you receive a few complaints, you will most likely see yourself disabled and even fired by your email service provider. Leading ESP's have a lower tolerance for spam and will try to keep their complaints to less than 10 per 10,000 emails. Shared IP addresses are suitable for smaller senders with fewer subscribers, and the sender does not have a consistent volume of sending emails.

  • Dedicated IP Address - Dedicated IP addresses are best for larger email senders sending a consistently high volume of emails. Companies sending more than 200k emails consistently per campaign would be a great candidate for having their IP address. Having a dedicated IP will allow you to control your email deliverability since only your campaigns will use that IP address. You can also use your dedicated IP to isolate and fix address deliverability issues, and you have more tools at your disposal to help you secure deliverability. Over time as you build your sending reputation, your IP will be a valuable asset. On the flip side, inconsistent sending patterns or dips & spikes in sending may lead you to be classified as a spammer. Also, dedicated IPs take a good amount of time to warm up, and if you are looking to start sending a lot of emails immediately, a dedicated IP is not the solution.

To pick the right IP strategy, you will want to take into account how many emails you are sending and will be sending and how vital sending emails is to your long term strategy. If you plan to send a lot of emails and build the core competency to make sure your emails are delivered successfully, you will opt for a dedicated IP strategy. If you are unclear of how many emails you will be sending and do not have time to manage your email reputation, you may want to start with a shared IP strategy. In the long run, a dedicated IP address will make the most sense if you are committed to building a strong email marketing strategy or have a lot of transactional emails.

Domain Address Matters and You Must Protect Your Main Domain

Your brand matters and your domain is your brand when it comes to email marketing. If your domain is listed on a blacklist, then all of your emails will likely end up in spam. Consequently, it is not a good idea to use your main domain for sending marketing emails. Look at the newsletters you receive; you might notice that most companies use subdomains, other extensions (com, io, and co..), or various domain names to prevent affecting their main domain from one single IP's bad reputation. If your domain gets blacklisted, you will have to follow the time consuming and uncertain process of cleaning up your reputation.

If you are uncertain if you should get a new domain, ask yourself this question: "Is there a risk that I may be considered a spammer by an ISP or one of my recipients?" If there is a risk at all, then consider using a new domain. For example:

  1. You just bought a domain, launched your website, and now you want to start emailing people. In this case, your domain has not been warmed up, and you are at a super high risk of getting blocked. You should buy a new domain similar to your main domain and use it for your emailing people. If your current domain is, then you can use

  2. You are a growing startup with an expanding sales team. If your sales team is growing, the number of emails you are sending will increase heavily. As new people get new email addresses, their emails will likely not be adequately warmed up, and your domain will probably be at risk. In this case, you should also buy a new domain for sending sales emails.

  3. You are an established company with an excellent domain. In this case, your company has built a fantastic sending reputation. You have invested a lot of time and effort to make sure you get high engagement with your senders. But, you have specific senders that have not engaged for over 90 days, or you want to reach out to customers that have left you, or you want to contact active prospects that have shown interest but have not engaged. In each of these cases, you run into a risk of being marked as SPAM, and in these cases, you should probably use a different domain.

Similar to an IP address, each domain needs time to earn a good reputation. Before purchasing a domain, make sure your domain is not blacklisted. You can use MX Toolbox ( or Neustar ( to check your domain status. You can create one or more domains for sending marketing emails if one of your domains ends up on a blacklist.

To start your domain will be added to four SPAM eating Monkey (SEM) blacklists that expire based on the domain's age:

  • SEM-FRESHZERO: For new domains created within 24 hours

  • SEM-FRESH: For domains registered within five days

  • SEM-FRESH10: For domains registered within ten days

  • SEM-FRESH15: For domains registered within 15 days

  • SEM-FRESH30: For domains registered within 30 days

If you start sending many emails, you will immediately damage your reputation since you are already being monitored. So ramp up slowly and make sure you have great engagement. Also, if you know, you will need to purchase domains for sending emails, make sure to buy them as soon as possible so they get out of SEM-FRESH.

For each new domain, make sure to set-up redirects or landing pages so participants can learn more about your company. Make sure to set-up Whois, Email Profile, DKIM, SPF, DMARC, TLS, and BIMI for the domain to make sure the domain is certified and authenticated. We will cover more about each of these authentication messages in the next article.

If you consider using a free email service like Gmail, AOL, or Yahoo for sending emails, we would highly recommend you do not do it. Using a generic domain will significantly increase your risk of not having your emails delivered (No DKIM, SPF, or DMARC); it reduces customer trust in your brand, making your interactions less professional.

Basic Principles Required To Maintaining A Strong Sending Reputation