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10 ways to improve and protect your sender reputation

Your email content is just the tip of the iceberg when it comes to building a great email program. Sender reputation – now that’s the impact hidden below the surface. WIthout a solid sender reputation, you can never hope to break through into the inbox. Check out our top tips.



What’s sender reputation? Glad you asked. In this article, we define what sender reputation is and its components, we’ll cover our top tips, and some of the most common mistakes that new senders can make.

Let’s dive in.

What is your email sender reputation?

Your sender reputation is a key factor that inbox service providers (ISPs) use to determine inbox placement – whether or not to place your email message in your user’s inbox or in their spam folder. In other words, your sender reputation is a major component of your email deliverability.

In a worst-case scenario (if your reputation is really bad), your sender reputation might even land you on an email blocklist. As you can imagine, sender reputation is very important. After all, whether you’re sending out a transactional email or an ecommerce campaign, what’s the point of great email design or personalized content if it never gets read?

ISPs aren’t always 100% transparent when it comes to their parameters for delivery and inbox placement. However, Gmail provides its Google Postmaster Tools that give you insight into what Gmail thinks about your sender reputation. Since Gmail is one of the major players in the email game, you can bet other email clients use similar measures to gauge your sender reputation.

What determines your sender reputation?

Just as in your personal life, it’s never a single action that determines your reputation. In fact, your sender reputation is composed of your IP reputation and your domain reputation over time.

  • Your IP reputation is based on the IP address from which you send mail. If you’re using a shared IP address, your reputation is also influenced by the other senders with whom you share your IP. On the other hand, if you’re on a dedicated IP address, you’re fully responsible for your IP reputation.

  • Your domain reputation is based on the domain from which you send mail, like Much like your IP reputation, your domain reputation is determined by the email you send from the domain.

Let’s unpack this for clarity. Here are some components that determine your IP and domain reputation, which, in turn, determine your sender reputation:

  • Email content: Are you sending high-quality emails that your subscribers want to receive? Email content that contains spammy characteristics or wording is flagged as low-quality emails. All-image emails and messages that are too large in size may also look like red flags to ISPs. You don’t want mailbox providers to think you’re a spammer.

  • Abuse complaints: Do your subscribers mark your emails as spam? This is called an abuse complaint. A high complaint rate might trigger spam filters and negatively impact your sender reputation. To avoid receiving abuse complaints, make it easy for your readers to unsubscribe when they no longer want to receive your messages.

  • Email list quality: Your reputation goes beyond your email content itself. For example, if you don’t maintain your mailing list through regular email verifications, you risk of having spam traps or invalid email addresses as part of your list. This results in a high bounce rate, which sends a red flag to mailbox providers because it appears like your content isn’t welcome.

  • Sending history: Okay, this one is a bit of a chicken-and-egg problem. If your IP address does not have a history of sending mail consistently, you’ll need to “warm up” your IP before you start sending email marketing campaigns at scale. Also, if you have a spotty sending history, you’ll be flagged as a potentially problematic sender. This, in turn, will cause problems for your email sending.

What are the consequences of being a bad sender?

So you’ve integrated your app with an email service provider (ESP). That’s it, right? Not quite.

If you’re using an EPS like Mailgun, we’ll help you protect your sender reputation. However, not all ESPs are created equal, and you may be on the hook for looking after your own sender reputation. If you have a bad sender reputation, ISPs will flag your messages and will be less likely to place your emails in your reader’s inbox.

Make sure your great email campaign reaches your reader’s inbox. Maintain a good sender reputation to ensure your email deliverability.

5 ways to improve your sender reputation

While you can use tools like Sender Score to monitor your sender reputation, that’s not enough by itself. Instead, check out these tips to improve your sender reputation:

  1. Maintain mailing list hygiene.

  2. Provide an easy way to unsubscribe.

  3. Use double opt-ins.

  4. Check if you’ve been blocklisted.

  5. Have proper authentication protocols in place.

Let’s go over each of these below.

1. Maintain mailing list hygiene

Verify your email list regularly to purge invalid addresses, spam traps, and disengaged subscribers. This lowers your bounce rate and increases your open rate. Both of these metrics will help improve your sender reputation.

2. Provide an easy way to unsubscribe

Avoid abuse complaints by giving your readers an easy way to unsubscribe when they want to opt out of their relationship with you. It’s sad to see them go, but that’s better than waiting for them to mark your messages as spam.

3. Use double opt-ins

Asking your subscribers to verify their emails before adding them to your mailing list might seem like an unnecessary extra hoop to jump through. However, this extra step helps to verify the email addresses on your mailing list are valid. More importantly, you give your users a chance to confirm they actually want to receive your messages.

4. Check if you’ve been blocklisted

Even if you’re a legitimate sender mailing high-quality content, you might end up on a blocklist. Check if you’re on a blocklist before sending out your next email campaign to ensure your messages land in your reader’s inbox. After all, if you’re on a blocklist, your messages will never make it to your reader’s inbox. A high bounce rate can negatively affect your sending reputation. At Mailgun, we provide a blocklist monitoring service to keep your deliverability high.

5. Have proper authentication protocols in place

Before you start sending, make sure you have your SPF, DKIM, DMARC, and BIMI records in place. These authentication protocols are your ID cards that prove you are who you say you are. Think of mailbox providers as the bouncers in a club. Your authentication records ensure you can join the party and stick that landing in your user’s inbox.

What are the 5 common mistakes to avoid?

From what we’ve explained above, you now understand what affects your sender reputation and how to keep it pristine. Let’s also expressly spell out the “don’ts” from the points we’ve touched so far.

  1. Don’t suddenly send a high volume of emails.

  2. Don’t send out spammy-looking content.

  3. Don’t forget to remove disengaged users.

  4. Don’t use a shared IP address.

  5. Don’t buy email lists.

Let’s dig into each of these below.

1. Don’t suddenly send a high volume of emails

As we mentioned above, suddenly sending out a large volume of emails sends a red flag to mailbox providers. This type of behavior is seen as “spammy” and can negatively impact your sender reputation. Instead, slowly warm up your IP for sending at volume. Some ESPs, like Mailgun, warm up your dedicated IP address as a service.

2. Don’t send out spammy-looking content

This goes without saying, but if it looks like spam, chances are that ISPs will treat it as spam. Don’t use all-image emails, spammy words, too many exclamation points, or too many emojis. If your message looks like spam, ISPs could refuse to place it in your reader’s inbox. This will negatively impact your reputation.

3. Don’t forget to remove disengaged users

Keep tabs on your email marketing metrics – like open rate, click-through rate, and conversion rate – to determine if your readers are still engaged. If your readers have become disengaged, you can send a re-engagement email or create a sunset policy to remove them from your email list.

4. Don’t use a shared IP address

As we mentioned above, using a shared IP means sharing your IP reputation with other senders. Of course, this can be a good thing if you’re a new sender and want to piggyback off of an IP with an established reputation. However, this can backfire if the other senders on your IP have bad email sending habits. Use a dedicated IP address to avoid these problems.

5. Don’t buy email lists

This is a surefire way to disaster. Purchasing email lists will likely lead to higher complaint rates – when recipients mark your content as spam, if the emails you purchased are all legitimate. Purchased lists are not validated, and the recipients on them have not opted-in to receive messages from your service. Even if you think these lists might contain some legitimate leads, the risk to your sender reputation is too high.

Wrapping up

And that’s sender reputation in a nutshell. If you’re not sure where to start when looking at your own deliverability, your in luck. We’ve got a team of account managers that can help evaluate and improve your deliverability program.

Learn about our Deliverability Services

Deliverability Services

Looking to send a high volume of emails? Our email experts can supercharge your email performance. See how we've helped companies like Lyft, Shopify, Github increase their email delivery rates to an average of 97%.

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