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Prevent your emails from going to spam with these 11 tips

Sometimes you start an email campaign with high hopes only to end up asking yourself: Why are my emails going to spam? Read more...



No matter how many stars we wish on, some questions will never have simple answers, and one of the most puzzling problems for any email provider is how to prevent emails from going to spam. Why does it happen? What can we do to stop it?  If you’re not sending spam, but your messages are still being flagged, this post is for you.

If your emails aren’t delivered to the inbox, it’s hard to get results from any email marketing program. But sometimes it can feel like Inbox Service Providers (ISPs) like Yahoo and Gmail have a vested interest in keeping you out of the very place your emails belong.

Still, as much as ISPs can seem like mean girls, they have a big responsibility in making sure their users see as little spam as possible. That means beefy spam filters. However, this doesn’t mean you’re powerless. Landing in the spam folder is something that can be avoided.

Are my emails going to spam? How to find out

When emails bounce or get blocked, you’ll know about it because it shows up in the reports from your email service provider (ESP). But if emails are delivered – but get filtered into the spam folder – how would you know? On your end, the system appears to have worked. But on the subscriber’s end, you’re just another grain of sand among the mass of spam emails that they select and delete.

One way to find out if your emails are going to spam is to use seed testing.

With a seed test, you send your first email to a small, carefully chosen segment of your subscribers and run an inbox placement test. You’ll eventually get data on where your emails went across the email addresses in the seed list.

If there are any issues, such as too many emails bouncing, not getting delivered, or ending up in the spam or promotions folders, you can work to address them before emailing the rest of your list.

Not every ESP allows you to send to a seed list. Sinch Mailgun does! Learn more about email seed testing with Mailgun.

Why do emails end up in the spam folder?

There are a number of reasons why this can happen, and not all of them are within your control. We’ll discuss these in more detail when we go through the various ways for how to prevent emails from going to spam.

A few of the reasons include:

Unengaged subscribers

If hardly anyone is even opening your emails, this data can cause inbox service providers to question your legitimacy as a sender. They don’t know you’re a spammer, but their data has given them enough reason to wonder, and you might get filtered into the spam or junk folder.

Spam complaints

The more subscribers who mark your emails as spam, the more likely it is for your future emails to be filtered there. If this keeps happening, and you’re getting too many spam complaints, you may end up on an email blocklist. But before that happens, you’ll start getting filtered into spam folders.

Bad sending domain or IP address

A poor sender reputation can lead to emails getting placed in the spam folder. Sometimes, your sender reputation could be due to previous behaviors you have exhibited with your email marketing. In other cases, if you're sharing an IP, that IP’s reputation may have already been tarnished by other senders, and you’re now suffering due to their actions.

That said, if you have a bad sender reputation, there are a number of potential causes. You’ll see some of them as we get into how to stop emails from going to junk.

11 ways to prevent your emails from landing in the spam folder

By implementing the strategies listed below, you can make great progress in reducing the number of emails that go to spam, so more of your subscribers see and can respond to your emails.

Use double opt-ins to acquire engaged subscribers

This is a common debate – require double opt-in and get fewer subscribers that you know really want to be on your list, or use single opt-in and get a bigger list, but have more subscribers with fake or unused emails addresses.

Double opt-in requires the subscriber to confirm they really want to be on your email list. After they sign up, they receive an automated email asking them to click to confirm they want to join your list. People who give fake email addresses or ones they never check, as well as spammers and bots, will not click to confirm.

If someone tries to sign someone else up for a list, for any reason including practical jokes, they won’t be able to complete the second step.

When someone does click that confirmation email, you know they’re a real person who actually wants to be on your list. That will result in higher engagement rates, fewer spam complaints, and all the other great benefits of email marketing.

Make your unsubscribe link easy to find

Unsubscribes are better than spam complaints. You should always include an unsubscribe link in your emails, in part because it will reduce spam complaints, since people will have another way to opt out of your list. It’s also required under most of the compliance laws, which we’ll discuss next. If you’re using Mailgun’s unsubscribe links, we’ll also add the “List-Unsubscribe” header line to help make that link stand out on platforms that support it.

Keep an eye on your engagement metrics

Over time, one thing about email marketing is as ironclad as death and taxes: Your list will atrophy. Metrics like open rates and click-through rates matter, because they indicate how well your content is connecting with subscribers.

People will unsubscribe, and people will become less engaged as your relevance or importance in their lives diminishes. That’s why you must continually refill your email list with new subscribers.

But, you also need to take steps to focus on your more engaged subscribers, and look at sunsetting your less engaged ones. At Mailgun, we call this strategic engagement.

For example, as people become less engaged, consider sending them fewer emails. Every so often, identify all the people who haven’t engaged with any emails in, say, six months, one year, and two years. Send fewer emails to each group in descending order. This will help sustain your open and click rates for the emails you do send, since the dead weight won’t be bringing down those metrics.

Conversely, you could start sending more email to your most engaged subscribers – this is called signal boosting. This can be risky depending on how much you’re already sending them, but for your biggest fans, it can also pay off.

And…keep them engaged – email consistently

Too many businesses will email a big welcome series, and then have no ongoing email marketing plan. Or, they’ll send a bunch of emails for a new campaign, and then send nothing for weeks or even months. This sort of inconsistency only hurts your engagement, because people forget about you and lose interest. Even your most fervent customers will abandon you if you don’t keep showing up consistently in their inboxes.

When engagement stays high, fewer mailbox service providers will treat you like a spammer, which is why keeping subscribers engaged is a great strategy for how to avoid email going to spam.

Use a reputable email service provider (ESP)

As mentioned earlier, some shared IP addresses have poor sender reputations because of how other companies have abused them.

Using a reputable email service provider such as Mailgun eliminates this problem, because ESPs are in the business of email, and we take proactive steps to ensure we are not the cause of our users getting bad sender reputations.

Clean your email list regularly

We get it. Sometimes it’s hard to let go of unengaged subscribers. But if someone isn’t engaged, it might be time to sunset them from your email list. Rather than just cutting them, send a re-activation campaign – ask subscribers who haven’t engaged in a while if they still want to receive your emails. Send them several such notices, not just one. For those who say they want off your list, or who don’t respond, remove them.

It’s also a good idea to make sure you have actual legitimate emails by verifying the email addresses of your subscribers. The best way to clean your list is with an email verification tool. InboxReady email validation allows you to simply upload your list and our program will run it against our send-databases to determine the quality and risk-level associated with each address. Our email verification tool is faster and more accurate than the competition because it uses real send data rather than a broken SMTP handshake. And if you want to stop bad email addresses at the gate, simply integrate our real-time address verification tool into your forms to keep your lists in perfect condition with no additional work needed on your end. Less time worrying about your lists means more time focusing on your core business. 

Do email verifications really drive ROI for your business? Customers using Mailgun Optimize Verifications have seen a 65% increase in opens and a 21% lower bounce rate!

Dashboard of bulk verification previews

Verify My List For Free

Focus on your email content

Don’t trick or mislead your subscribers with deceptive email subject lines. And proofread your emails. Spammy emails usually have typos and bad grammar. If your emails look like spam or put a bad taste in the subscriber’s mouth, more of them will mark it as spam.

Avoid spam trigger words, these are phrases that trigger spam filters because of their common use in phishing emails or spam content. A good practice is to think of how an old infomercial or a self-help book would say it and then do the opposite. Leave phrases like as seen on, act now, act fast, be the best you, etc.

You also want to make sure your email is properly coded especially when it comes to HTML. It’s helpful to look over your code to be sure nothing is out of place. Using a campaign precheck process will ensure your emails look perfect across dozens of platforms and devices.

Want to know more about how to get your emails in the inbox? Check out our Email Growth Playbook, a database of 60+ tactics to help you improve the performance of your email campaigns.

Avoid spam traps

Spam traps are fake, discontinued, or abandoned email addresses that have been repurposed by anti-spam services to catch spammers. If you send emails to a spam trap, and continue to do so, this tells them that you’re not monitoring your metrics or email reporting data – another hallmark of spammers.

At best, this will make your emails get marked as spam. At worst, it will land you on a blocklist and start derailing your email deliverability – an even worse problem than getting filtered into the spam folder.

How do you avoid spam traps getting on your email list? The answer is the same as before –use an email verification tool. With email verification, you’ll know if an email address has gone bad and can remove it immediately.

Spam Trap Monitoring from Mailgun Optimize provides insight into how often you are sending to pristine, recycled, and typo spam traps. Identify issues in near-real-time so you can protect your sender reputation and avoid serious disruption to your email program.

Ask subscribers to whitelist your email address

This should be a standard part of any welcome email series, because that’s the time subscribers are most likely to take this step. Bear in mind that many people won’t know how to do this and won’t want to learn. You can try to reach them by using more helpful language.

Say things like “please add us to your contacts,” or “make sure our emails don’t land in your spam folder and add us to your trusted senders list.”

With modern spam filters sometimes your recipients don’t even have to mark your message as spam for it to go there. Something as simple as the word “free” in your subject line can get your message sent right to the spam folder. With Mailgun Optimize Inbox Placement you can see which folder your email is most likely to land in before you send. This makes it easy to identify spammy content, iterate, and deliver a high-impact campaign.

Provide an email preference center

This takes some setup work, but it’s worth it, especially if you send a lot of email or have several functioning and distinct segments based on interests, product categories, or other criteria.

Let people decide if they want one email every day, or a one a week that summarizes the daily emails. Let people choose which of your main email segments they want to be on. Make it easy for them to customize their preferences, and they will be more engaged and less likely to mark you as spam.

Use email authentication

When mailbox service providers like Yahoo and Gmail, as well as services like Microsoft Outlook, can verify that your emails really are coming from your company, you’ll be far less likely to be sent to spam or junk folders.

Email authentication takes a little work to set up, but your email service provider should be able to help. The main authentication methods are SPF, DKIM, and DMARC, all of which take quite a bit of time to explain. For now, just be aware that you should put this on your list to attend to if you want to do more to prevent your emails from being marked as spam.

Send emails at the right time – send time optimization

Different people tend to open and read emails at different times. Some like to start their day by running through their emails. Others do it before leaving work. Others do it at lunch, or in the evenings. Others save it all for one or two days per week.

You’ll increase your email engagement if you send emails closer to the times when each subscriber is likely to be looking at them. This is called send time optimization, and with Mailgun, you can apply this tool to each person on your email list.

Again – engagement prevents your emails from going to spam. Send time optimization is another tool that increases engagement.

Preview before you send

You spend weeks working on the perfect email only to find it didn’t render properly on your recipients' most-used devices. Emails like this are much more likely to be marked as spam and get lower engagement, eventually damaging your sender reputation. And with so many devices and email clients out there, it can be nearly impossible to know how your email will look on each one.

Email previewing allows you to upload your HTML and see exactly how it will look on more than 90 different devices and clients before you hit the send button. You won't have to worry about last-minute rendering issues causing major issues.

Make sure you’re compliant

The acronyms never stop, and when it comes to email compliance, they’re having a heyday.

But these email compliance laws are no joke. If you have subscribers in places like Canada and Europe, you have to follow their anti-spam laws, even if you don’t have a physical presence there. The good news is, most of their requirements are similar, and most ESPs already help you meet them. Also, if you’re using the ideas in this article for how to stop emails from going to junk folders, you’ll be complying with anti-spam laws.

The CAN-SPAM act states that you have to get a subscriber to opt-in to email messages that you’re sending to them for marketing reasons. Using double opt-in goes beyond this. CAN-SPAM also requires you to make sure your email is properly labeled and not misleading as to who sent it and why. And, you must include privacy policy links and a physical address on your emails.

The European Union’s General Data Protection Regulation (GDPR) requires you to ask for clear consent from your subscribers before sending any marketing communications. The state of California has a similar regulation: the CCPA.

Following these laws helps you steer clear of the spam filters and stops your emails from going to spam.

Wrapping up: care about your subscriber relationships

Aside from deliverability issues, winding up in the spam folder drastically limits your ability to communicate with customers and users. The good news is that the common reasons for being flagged as spam that we’ve outlined are easy to avoid. And following these best practices will automatically reduce a lot of general deliverability issues.

If you think you need some help with improving your emails, our managed email deliverability service might be a great fit for you. You get a cool Technical Account Manager, and we’ll help you learn the ins and outs of email and do everything possible to prevent your emails from going to spam.

Mailgun Optimize makes email deliverability easy

Get a suite of tools and services that drive campaign performance and boost the ROI of your email program.

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