What Is Email Domain Reputation and How To Improve It

What Is Email Domain Reputation and How To Improve It
04 May, 2022 • ... • 1487 views
Eugene Vasilev
by Eugene Vasilev

Email domain reputation is one of the most fragile things in email marketing. Like with any kind of reputation, it takes a lot of time to build up but it can take just one moment to ruin everything.

In this guide, we tell you about the main dangers to domain reputation, ways to check it and tips to keep it high.

What is domain reputation and how does it impact deliverability?

An email domain is the part of an email address that comes after the @ symbol.

For example, when you send personal emails via Gmail, your domain is gmail.com. If you’re a business, your company likely has a designated domain that often matches the website address.

email domain
Morning Brew sends newsletters from their domain

A domain reputation is the overall condition of a domain. To a great extent, it influences email deliverability — all emails you sent minus bounces and spam complaints. Domains with good history and reputation have a higher chance to have their emails delivered to subscribers’ inboxes instead of spam folders.

Conversely, senders with a bad domain reputation may even see their transactional emails end up in the spam folder.

The domain reputation along with the IP address reputation (the condition of the IP address) make up the sender’s overall reputation. Don’t assume that a new IP address will fix a damaged domain reputation. While the IP reputation can be reset with a new IP address, the domain reputation stays with you even when you change a device.

How is domain reputation calculated?

Mailbox providers (Gmail, Outlook, Yahoo, etc.) measure a domain reputation on a scale from bad to high. Points are added or deducted for each mailing.

The better your reputation is on the scale, the more email services trust emails coming from your domain and put them into inboxes. How exactly mailbox providers award points is unknown because they keep it secret for safety reasons.

There are obvious factors that influence reputation in a negative way. For example, senders without email authentication won’t shake a poor reputation off unless they get verified. Doing email blasts without special email software will also be no good for the sender’s reputation.

Other things that impact the domain reputation are less obvious and we talk about them next.

5 dangers for domain reputation

Whether you’ve just set up a new domain or been using one for a long time, there’s a list of practices to avoid to keep a domain reputation high. Since a domain reputation is hard to repair, it’s vital to avoid these things.

Poor email practices

Mailbox providers know the look and feel of spam because they analyze literally (yes, literally) every email and see if it has anything in common with spam. Here are some of the most common red flags for mailbox providers:

  • Low engagement. If the open rates stay low and spam complaints go up, it means that subscribers don’t find value in the content and the overall engagement goes down. Even when the content is good, when it comes to the wrong audience, people don’t engage with these emails.
  • Trigger words. Mailbox providers don’t like senders who make unrealistic promises. These words are typical of subject lines.
a list of spam words
Source: Overdrive Interactive
  • Lazy design. Spammers don’t pay attention to design, so even in the age of good-looking emails, their emails look messy like cable TV guides from the early 2000s.
an example of a spam email
Source: Securelist
  • No mobile version. This is a signal to mailbox providers that senders don’t pay enough attention to emails.


Mailbox providers create blacklists to tackle spamming. Senders who get blacklisted can no longer reach inboxes which is a major blow to deliverability and a domain reputation.

Senders get blacklisted when too many recipients mark their emails as spam or junk. It may take just one email with too many complaints to blacklist the sender’s domain.

Spam traps

Spam traps are also called honeypots, only the honey isn’t sweet. A spam trap is an email address used exactly for the purpose of catching spammers. There are three types:

  • Pristine traps — fake email addresses created by mailbox providers. They don’t belong to any person which means that whoever has these in their database has shady ways of building a contact list.
sites selling contact lists
A contact list bought on the internet is a hotbed for spam traps
  • Recycled traps — real email addresses abandoned long ago. Mailbox providers claim inactive emails after a period of inactivity, usually around a year. Senders who don’t clean their database can be caught this way.
  • Typo traps — misspelled email addresses in a contact list: gnail instead of Gmail or Yahho instead of Yahoo, etc. If a sender has these in a database, it’s a signal to mailbox providers that the sender doesn’t maintain the list hygiene.

Hitting a spam trap is often the main reason for being blacklisted. Unlike spam complaints and bounce rates, spam traps are hard to identify. The best way to tackle them is to prevent them from getting into your database by using legal ways of building a contact list.

Inconsistent email practices

Mailbox providers are suspicious of sudden changes in senders’ behavior because inconsistent mailing is typical of spammers. That’s why legitimate email marketers plan their campaigns while spammers don’t care about reputation and only want instant results.

Here’s some inconsistent behavior that mailbox providers may consider suspicious:

  • Sudden changes in volume — when one day you send emails to 5% of your subscribers and the following day to 100%.
  • Inconsistent pace of mailing — when you send emails twice a week, then go quiet for months, then start mailing every day.
  • Different content — when your content has radically changed: a clothing company now sends emails about cat food.

Too many emails from a new domain

Mailbox providers believe in natural growth. That’s why they don’t see it as normal when new domains start sending mass emails straight away.

According to their logic, senders with new domains can’t have many subscribers, and if they do, the contact list was bought. It takes time to build a domain reputation up to look legit in the eyes of mailbox providers.

How to check domain reputation

Mailbox providers have analytical tools called postmasters. They analyze deliverability, spam complaints, IP and domain reputations. Gmail, Outlook, Yahoo — each popular mailbox provider has its postmaster.

One of the most popular postmasters is Google Postmaster Tools which analyzes emails sent into Gmail mailboxes. It ranks a domain reputation from bad to high:

  • Bad. Emails from this domain will either be blocked or marked as spam because the sender received too many spam complaints.
  • Low. Emails from this domain will most likely be marked as spam because of their overall low quality.
  • Medium. Spam is occasionally reported from this domain but it’s mostly good. Such emails will have good deliverability except for periods when spam complaints go up.
  • High. The reputation is near spotless. Emails from this domain are unlikely to be marked as spam.
postmaster interface
Good domain reputation vs bad domain reputation in Google Postmaster. Sources: SocketLabs, Unione

Apart from Google’s Postmaster, you can consult these sources for checking your domain reputation:

  • Talos Intelligence. Talos checks both email domain and web reputations. In addition, if you run your domain through Talos’ database, it’ll show details on its history.
  • BarracudaCentral. Barracuda is committed to providing technical details on internet security. The service manually verifies all IP addresses and domains with a poor record.

Tips on how to improve domain reputation

Here are the best practices to keep your reputation high and avoid potential pitfalls.

Use double opt-in

A double opt-in is the process of getting an extra confirmation of an email address from a subscriber.

This extra measure assures the quality of a contact list. If a subscriber is willing to confirm an email address, he or she is genuinely interested in hearing from you.

The alternative is a single opt-in but this is the quantity vs quality debate. Single opt-in advocates argue that it’s a faster way to grow a contact list. Sure enough, but there are dangers associated with it: fake accounts, spam traps and misspelled email addresses end up on a contact list with a single opt-in.

an example of a single opt-in
A gnail.com address has just been added to this company’s contact list via a single opt-in. At best, they’ll spot and remove it. Otherwise, it’ll impact their deliverability and reputation

That’s why a double opt-in is a more secure approach. This makes sure your contact list is legit and it’s pretty much impossible for spam traps and misspelled addresses to get in.

an example of a double opt-in email
A double opt-in confirmation

A full list of advantages, law requirements and how to set it up in Selzy — we’ve got you covered on these topics in our guide on double opt-in.

Don’t hide the unsubscription option

No one likes to lose subscribers but an unhappy subscriber is a potential source of trouble for your domain reputation. If people no longer want to hear from you — fair enough, give them a clear way to unsubscribe.

Obfuscating the unsubscribe link can only anger a subscriber. No one’s going to study an unwanted email for the unsubscribe link when it’s easier to send it straight to spam.

an email with a bad unsubscribe link
Not only is this unsubscribe button hard to notice but it’s also not working. A spam-folder offense. Source: Reddit

Unsubscribe links are usually placed in an email footer. The button doesn’t have to be large like a big banner — just visible enough and clickable.

an example with a good unsubscribe link
A typical unsubscribe button is placed in the footer with the link underlined

Unsubscribing benefits both the recipient and the sender. The recipient no longer receives irrelevant content and the sender doesn’t waste time on uninterested subscribers who undermine the deliverability and reputation.

Complete guide on unsubscribe links: the best practices, templates and ways to punish senders who don’t add those links (😈)

Avoid spam words in the subject line

Emails with spam words in the subject line risk not reaching customers’ inboxes because mailbox providers see them as suspicious. Here are some examples:

  • Clickbait phrases with unrealistic promises
  • Money symbols
  • Excessive punctuation
  • Emoji jumble

Even if such an email slips through a spam filter and lands in an inbox, the recipient may not be baited into opening it. If the recipient opens it and doesn’t like the clickbaity look of it, the email has a good chance of going to the spam folder. Either way, it’s a blow to the sender.

How to write compelling subject lines with a positive impact on KPIs — read in our guide.

Do regular email list clean-ups

List hygiene has a direct impact on your deliverability and domain reputation.

You may use a double opt-in and be sure your contact list is full of top-quality subscribers but if they stop reading you, they’re as useful as fake jeans pockets. In fact, inactive contacts may be abandoned addresses — time bombs set to turn into spam traps. By regularly cleaning your list up you remove inactive contacts and thus increase deliverability.

Selzy’s tool to check contact lists

Selzy has the “Check contacts” tool that helps you find inactive contacts

How regular should clean-ups be? It depends on the volume and frequency of your mailing. If you send emails every day or almost every day (e.g. newsletters), look with suspicion at contacts that don’t react to you for a couple of weeks. If you send just a couple of emails per month, this period can be longer.

We recommend clean-ups every 2 to 6 months to maintain list hygiene, keep deliverability high and protect domain reputation.

How to keep your contact list clean and improve deliverability? Read in guides on list hygiene and trusted ways to clean a list.

Review your statistics to identify trends

Use analytics provided by your ESP of choice to track engagement rates through stats like open rate, bounce rate and spam complaints. This will help you see if subscribers find your content engaging and if there are any problems with deliverability.

Selzy’s analytics dashboard
Selzy’s dashboard shows campaign details: opens, click-through rate, spam complaints, etc

Meanwhile, tools like Google’s Postmaster will give you a detailed overview of how your domain and IP address perform.

By making the most of available resources, you’ll get the best look at your email marketing performance, including your domain reputation.

Avoid getting blacklisted

A blacklist is a list of IP addresses and domains suspected of sending spam. Even if you’re convinced that you only send high-quality content, this alone isn’t enough to stay clear of blacklists.

Tools like MXToolbox or Mailtester will help you see if your domain is listed on any popular blacklist.

a blacklist test
An example of an email tested through MailTester

To minimize the risk of getting blacklisted you need to combine the best practices listed above: a double opt-in, list hygiene, an easy-to-see unsubscribe link, and overall good quality of your content.

Ensure that all the authentication techniques are in place

Email authentication is needed to verify the authenticity of the sender. Mailbox providers require it to make sure the sender is not a spammer.

Verified senders enjoy two benefits:

  • Deliverability guarantee. Non-verified senders receive a low reputation rating by default and have issues delivering emails to subscribers’ inboxes.
  • Postmasters access. Mailbox providers give access to their postmaster tools only to verified senders.

Email authentication includes three protocols: SPF, DKIM and DMARC.

  • SPF (Sender Policy Framework) shows which IP addresses are permitted to send emails from your domain. The recipient’s server checks the SPF to decide where to put the email: inbox, spam folder, or to block it.
  • DKIM (DomainKeys Identified Mail) adds a digital signature to your domain. Thanks to it, mailbox providers can see that an email is authentic and sent from a verified source.
  • DMARC (Domain-based Message Authentication Reporting and Conformance) checks SPF and DKIM. For example, if a sender doesn’t have DKIM, the DMARC protocol may block the email or send it to the spam folder.

Set up authentication in your ESP of choice. You can do it by yourself in Selzy’s personal account or have it done for you by ordering the service — just contact us through the chat for help.

Warm up your domain

Mailbox providers are suspicious of emails from new domains and IP addresses because every new address is a potential spam threat. Under a bit of suspicion, an email goes to the spam folder.

To look legitimate to mailbox providers, it’s important to create a domain reputation by warming a domain up. The logic is simple: mailbox providers believe in natural growth and to them, new domains can’t have many contacts.

A warm-up is a gradual process. At the start, you send a few emails to a small audience. For example, transactional emails only. As time goes by, your audience and email frequency grow.

The warm-up can take up to two months. Old domains usually don’t need it, especially if the sender sticks to a consistent schedule.

Week Number of recipients % of contact list
1 2,500 5%
2 5,000 10%
3 10,000 20%
4 15,000 30%
5 25,000 50%
6 35,000 70%
7 40,000 90%
8 50,000 100%

What a warm-up schedule may look like

Use subdomains

A subdomain is related to your domain but mailbox providers treat it separately. That’s a great solution when you want to prevent different email types from affecting each other.

email subdomain
Source: Litmus

If one of your subdomains receives spam complaints or gets blacklisted, it’s less likely to impact your main domain than if you used one domain for all email activities.

Subdomains are often used in transactional emails. No one wants emails like payment confirmation or password reset to land in the spam folder, that’s why it’s practical to separate them from the rest.

Some use a subdomain for sending promotional emails to save the root domain from potential trouble. If a promotional email receives many spam complaints it won’t affect the main domain.

Key takeaways

An email domain reputation is the overall condition of your domain. It’s one of the factors making up the overall sender’s reputation.

It’s a crucial factor to deliverability: good reputation = higher chance of good deliverability. For senders with a bad domain reputation, even transactional emails will go to the spam folder.

You can track the domain reputation with postmaster tools, for example, Google Postmasters Tools. Points are added or subtracted for every mailing.

A number of factors negatively impact the domain reputation. To prevent it from happening, rely on proven solutions listed in this table.

Threats to domain reputation ✅ Solutions
Poor emailing practices Higher content quality

Easy unsubscription

Regular stat checks

No spam words in the subject line

Getting blacklisted Email authentication

Regular email list clean-up

Use of subdomains

Spam traps Double opt-in
Volume inconsistency Planning campaigns ahead
Too many emails from a new domain Domain warm-up
04 May, 2022
Article by
Eugene Vasilev
Content writer on all things email marketing at Selzy. Writing, editing and illustrating over the last 5 or so years. I create simple texts with examples to inform or entertain readers. In love with the semicolon. Boring language merchant. Egg came first. My favorite bands will never come to my city. Let's play beach volleyball.
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