Your trustworthiness as a brand is crucial. When it comes to email, this is no different. A positive sender reputation allows mail servers to know you send safe, high-quality, and relevant messages. It can be the difference between landing in the spam folder or your recipient’s inbox. But how do you make sure your sender reputation is good? A lot of it comes down to following some best practices and using good ol’ fashioned common sense.

A Clean Database

A clean database is half the battle. Are you actively removing outdated emails? Have your recipients opted in to receive your marketing? Your database is the backbone of your email marketing strategy.


Relevant content and well-written texts: to optimize your sender reputation your readers need to enjoy receiving your mail.

Domain & IP Reputation

All the factors we will discuss today are eventually reflected in your domain and IP reputation. These categories together define your sender reputation.

Reputation Scores

Each mailbox provider has its own complex algorithms to determine what emails are safe for its users, weighing the numerous factors affecting your reputation differently. It’s hard to know the exact differences between email clients or what factors that weigh the heaviest, but there are several third-party authorities you can use that will analyze your sender reputation and provide you with a score “guesstimation”.

You have a particularly large influence on your domain reputation. By using AllClients CRM, you have a team dedicated to managing your sending IP address, which means we’re upholding the highest IP reputation for your senders and you won’t need to worry about that.

Factors for Domain Reputation

Complaint Rate

As soon as a recipient marks your mail as spam, a complaint is made. A high complaint rate can have drastic short and long term consequences on your reputation and deliverability. A complaint rate below 0.1% is acceptable.


Mailbox providers and third-party tools check if your IP or domain is on any known blacklists, which are lists containing thousands of known spammers and abusers. It’s a lot easier to get on a blacklist than it is to get off of one, but not all blacklists affect your reputation in the same way.

Inactive Addresses and Bounces

Remember the importance of a clean list? Mailbox providers check how frequently you email inactive addresses. Inactive means the email address no longer exists or is no longer in use. Particularly hard bounces, when the reason the mail cannot be delivered is permanent, have a big impact on low sender reputations. Soft bounces, which can for example be caused by full mailboxes, can turn into a hard bounce after so many attempts. High bounce rates indicate you don’t clean your list or may have built your list not using best practices, for example by scraping websites or purchasing lists.

Spam Traps

Spam traps are email addresses that will mark any mail they receive as spam. These addresses are either long abandoned and eventually converted by the mailbox provider, or were created specifically to be spam traps, then hidden within the code of websites to punish scrapers, or provided to database resellers as “honeypots”. As they do not actively sign up for any marketing, legitimate senders who are following best practices would never send them an email.

Temporary Addresses

These bot-generated, single-use email addresses can be used to sign up for services, make purchases, or access your lead magnet’s content. They pollute your list as they are worthless and sending to them will only lower engagement or increase your bounce rate.

Sending Volume and Cadence

Great sender reputations don’t come overnight. Brand new domains with little to no history that suddenly send high amounts of emails will get marked as spam a lot sooner. This means you need to take your time to warm up any new domain before blasting out at full speed, this can even be relevant for older systems. For example, if you usually email 20,000 contacts and suddenly email 400,000, it could harm your reputation. Gradually build up your email volume and send with consistent frequency.

Email Security and Authentication

DKIM and SPF will help legitimize you as a sender and protect you against abusers. It’s not surprising that having these protocols on your domain help you improve your domain reputation.

Importance of Content

It is generally agreed upon that mailbox providers factor in IP and domain reputation more than the content of your email. Content-based spam filters cause a lot of false positives, seeing legitimate emails as spam. Nevertheless, it can impact your deliverability.

Text-to-Image Ratio

There is an ongoing debate on the ideal ratio of image to text in marketing emails. Various numbers have been represented, ranging from 60-40 to 80-20 text to image. Admittedly most of the debate isn’t necessarily about deliverability but emails consisting almost exclusively of images do get sent to spam a bit more. Additionally, it’s bad practice considering some email clients have images turned off by default, so your readers may open your email and see nothing.

Avoid Spammy Words

Spam trigger words are a thing. Including a lot of dollar signs, promises of free gifts, or the secrets to earning more money. Your email may not be junk, but if you notice any parallel content between your emails and what you find in your spam folder, there is a chance that the algorithms think it could be junk. As we’ve mentioned, content-based spam filtering isn’t the go-to and you shouldn’t worry about including a dollar sign in your legitimate email but combining an email filled with spam trigger words and a low sender reputation might push you over the edge and into the spam folder.

High-Quality Content

We’ve mentioned it before, you need to send emails your recipients want to read. If your readers are highly engaging with your mail, this will benefit your sender reputation. On the other hand, if you’re sending emails your readers aren’t interested in, you’ll see a rise in complaint rate. Even if you exclusively email opt-in contacts, readers can still report you as spam if they don’t feel the emails are relevant to why they signed up or if they’ve simply forgotten they gave consent and dislike what you send. Many people frivolously click the “spam” button and don’t think about how it affects you as a sender.


There are countless factors that have some influence on your sender reputation. Due to advanced technology and an ever growing amount of spam emails being sent each day, it’s an ongoing battle between spammers and mailbox providers at the cost of legitimate senders.
But just because we can’t know exactly what goes into reaching the inbox doesn’t mean you can’t understand the basics and take control of your reputation as a sender.

Use what you’ve learned to stay on the good side of both mailbox providers and your readers. And if you dislike shooting in the dark, prioritize your work and join forces with a CRM like AllClients and let them deal with the logistics so you can soundly focus on effective engagement strategies.

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