Cold Email · · 6 min read

7 Proven Strategies To Prevent Emails From Going to Spam

Strategies like warmups, domain authorization, and validation prevent emails from going to spam. But why do emails end up in spam in the first place?

prevent emails from going to spam

It's incredibly frustrating when well-thought-out and personalized emails go straight to spam. Not only do you lose potential leads, but you also damage your email reputation.

There are two main issues to look out for—leads manually tagging our emails as spam and email service providers like Gmail or Outlook sending our emails straight to the spam folder.

Following email best practices prevent these issues. But sometimes, adjusting subject lines and CTAs isn't enough. Technical settings like DMARC, DKIM, and SPF also need consideration.

We're here to help you tackle all of these. By the end of this guide, you'll be able to prevent emails from going straight to spam, improve open rates, and boost overall conversions.

But first, we need to understand:

  • Why our emails go to spam
  • The adverse effects of spam on sending accounts
  • Strategies to prevent emails from going to spam
  • Email best practices to follow

Why Do Emails Go to Spam?

Spam emails can be any email sent in bulk with malicious intent. Bots send most of these, but humans can also send spam emails. These come from unsolicited, non-personalized emails.

It could be your subject line, email copy, or certain words or phrases like "free" or "meet singles" that make it "spammy." Here are the most common causes you should look out for:

Your Emails Were Tagged as Spam

When enough people mark your emails as spam, service providers can automatically send your emails to the spam folder. Let’s say most of the leads from your email list use Gmail.

Even if most of your leads didn’t flag you, your emails could still be in the spam folder for all Gmail leads. Unfortunately, there isn’t much we can do at this point.

But as they say, “prevention is better than the cure.” So, as the bare minimum, ensure that your emails don’t contain any trigger words or phrases.

Spam Filter Trigger Words and Phrases

All email providers use machine learning to know what’s spam and what isn’t. The spam list is updated daily as users send emails to spam. Watch out for these words/phrases:

  • As seen on
  • Billing Address
  • Cancel at any time
  • Direct email
  • Explode your business
  • Free (and its variations)
  • Gift card
  • Hello
  • Important information
  • Legal notice

Spam trigger words in subject lines or email bodies can automatically send your emails to spam. Avoid these words/phrases for a higher chance of emails being sent to an inbox.

Your Emails Have No Opt-Out Options

Even if you’re emailing leads that opted-in to your email list, newsletters, or subscriptions—having no option to opt-out or unsubscribe can put you in spam.

For example, the U.S. has the CAN-SPAM law that states emails need options to unsubscribe. It also says that you must process the unsubscription within ten days.

While it might look negative, unsubscribe links help qualify leads showing genuine interest in your offerings or content. More importantly, it enables you to keep a clean and healthy email list.

Emails Have Too Many Attachments

Be very careful when it comes to attachments. Some service providers, as a precaution, tag emails with attachments as “potentially harmful.”

While that doesn’t automatically send emails to spam, it could be enough to cause recipients to flag it manually. To avoid this issue, don’t send emails with attachments.

If it’s essential, inform recipients ahead of time. For example, if you’re sending a cold email and want to show a case study, you can ask leads: “Is it okay if I send you our case study?

When you do send an attachment, upload it to cloud storage providers like Google Drive. Then, attach the link to your email.

Email Domain Authentication Isn’t Set-up

If you’re running cold email campaigns, domain authentication is a must. You must have three main authentication types: DMARC, SPF, and DKIM.

Setting up DKIM provides your emails with a digital signature, verifying each email. SPF verifies your sending IP against a list of approved ones. Once both are set up, you can enable DMARC.

Although it does get technical, setting them up is relatively easy. In the next section, we’ll learn how to set this up and other strategies for preventing emails from going to spam.

Strategies for Preventing Emails From Going to Spam

As mentioned earlier, there are dozens of reasons why emails end up in spam. But whatever the case may be, following these strategies ensures the highest chance of emails going to an inbox:

Setting Up Domain Authentication

Even with the best sales email templates, personalization, and high-value content, your cold email-sending accounts can still be flagged as spam without domain authentication. Before enabling DMARC, we need to set up SPF and DKIM.

Follow the steps for Google or Office 365 to set up SPF.

For DKIM, refer to this guide for Google and Office 365. Ensure that your “service provider-recommended DKIM Selector” is set up as:

  • “google” for Google/Gsuite
  • “microsoft” for Office 365
  • “default” for other providers.

To check if DKIM is working correctly, use this tool. It typically takes 48 hours for DKIM and SPF to authenticate messages for your domain. Then, you can turn on DMARC.

You can choose either Google or third-party providers like Postmark to enable DMARC. After everything’s set up, use this tool to check whether or not DMARC is successfully enabled.

But even with everything set up perfectly, running cold email campaigns can quickly get your domain or IP blacklisted. We can easily prevent this by running email warmup campaigns.

Warming Up Email Sending Accounts

how to prevent emails from going to spam

Email warmups help signal to email providers that your accounts are legitimate and trustworthy. Instantly offers automated and unlimited warmups for unlimited sending accounts. All it takes is a few clicks.

When warmups are enabled for sending emails, Instantly automates positive conversations across a large pool of users who are also warming up.

This signals providers that the emails you send are worth opening, which ultimately helps your cold emails avoid spam filters. But before sending emails, ensure your email list is validated.

Validate Email List

Consistently emailing inactive addresses is a surefire way of inflating your bounce rate. We don’t want that happening. Make sure each email is validated before hitting send.

Use email validator tools to help automate validation. But if you want to run campaigns with already validated leads, you can try the Instantly B2B Lead Finder.

With Instantly, you only pay for validated leads. Plus, you get several advanced options to get leads that qualify or fit your buyer persona or ideal customer profile.

After validating your email list, you next need to personalize your emails. You can use templates or personalized spintax.

Personalize At Scale Using Spintax

You can create multiple variations of your email copy using spintax. This is essential as you don’t want to send the same email to hundreds or thousands of recipients. Do you know what that looks like?—Spam! We can create spintax for free using tools like ChatGPT.

Spintax can be used on every part of an email. Let’s say you’re a SaaS company that built a low-cost solution for inventory management for medium to enterprise-level eCommerce businesses. The email subject you thought of is “Stop Losing Sales to Stockouts.”

We can use spintax for the pain point {{stockouts}}. Here’s the example prompt we used and the output for the spintax.

Comply With Internet Privacy Laws

Countries like the U.S., Canada, and the UK have strict laws regarding internet privacy, data collection, and how personal data (like email addresses) are used. The most important include CAN-SPAM, CASL, GDPR, and CCPA.

Common themes across these laws include clearly stating why you’re emailing, ensuring opt-out options, and ensuring the email addresses are gathered with consent or from publicly available information.

Optimize Sending Addresses

Sending cold emails at scale requires creating alternate or burner domains for your sending accounts. This protects your main domain from the potentially harmful effects of cold emailing.

But you can’t just use any random sending address. Remember, your address appears in a recipient’s “From” field. As a rule of thumb, don’t use numbers or characters.

For example, if your main domain is “,” you can use alternate domains using top-level domains like “,, or”

Proofread Emails

This feels like a no-brainer, but it happens to the best of us. Make sure you proofread your emails, especially those written with the help of AI.

You can always personalize emails at scale with AI. But ensure the output is relevant with the proper information in place. Fact-check everything.

Look out for typos, grammatical errors, or sentences that don’t sit right with you. Free tools like Grammarly can help you streamline much of the proofreading process.

Key Takeaways

We can’t 100% prevent our emails from going to spam. However, following the right best practices and strategies ensures us the highest deliverability rates and protection for our sending accounts. As a quick refresher, here’s what you need to know to help you prevent emails from going to spam:

  • Avoid using spam words in any part of your email
  • Set up domain authentication (DKIM, SPF, DMARC)
  • Warmup emails before starting campaigns
  • Use spintax to create variations of email copies
  • Comply with Internet Privacy Laws

With best practices in place to help your emails land in your prospect’s inbox, all that’s left is to use the right email tool to scale. That’s where Instantly comes in. Sign up for free today!

Read next

10x your leads, meetings and deals.

Instantly scales your outreach campaigns with unlimited email sending accounts, email warmup, B2B lead database and generative AI