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Don't Let Your Cold Emails Get the Cold Shoulder: Tips to Stay Out of the Spam Folder

Updated: May 20

Have you seen a steep drop off in email engagement metrics?

Emails bounce or end up in the spam folder?

It’s most likely that you’re having some issues with your email deliverability and email sender’s reputation. Recent changes by Google and other email service providers (ESPs) in how they filter and prioritize emails have made understanding deliverability more crucial than ever.

A (Brief) History of Unwanted Email

The battle against spam has been ongoing since the dawn of email time - specifically, 1978, when the first commercial ad was sent to 400 (out of 2,600) users of ARPANET.

Spam took off in the 1990s and 2000s thanks to open relay systems, where emails could bounce around from any sender to any receiver. The web was also booming with content and people started using link farms to skew search results, pushing the need for the first spam filters.

We won't go through the whole timeline of botnets and Nigerian Prince scams, but suffice it to say that the rules and regulations of today make it increasingly important to get a handle on your email health.

Understanding Email Deliverability

Deliverability is the cornerstone of successful cold email, influenced by factors like sender reputation, recipient engagement, and the technical setup of email campaigns. Understanding the nuances of how ESPs track and measure deliverability metrics (open rates, click rates, spam complaints) is essential for any sales or marketing expert looking to optimize their email strategies.

Most Important Rule: Never Send Cold Emails From Your Primary Domain

We cannot stress this enough.

Sending hundreds of cold emails from your primary domain is a surefire way to get flagged as spam by Big Brother. Instead, you'll want to set up multiple, separate domains to send from.

Let's take Main Street Co. as an example. Main Street Co.'s primary domain is If they wanted to start sending cold email, they would set up two separate domains: and

Then, they would set up at least at least two email inboxes per domain, per person (, That way, if one email gets marked as spam, there's a backup.

It’s not a bad idea to set up a few extra emails and domains, too. This allows you to switch domains or inboxes if issues emerge. Shoot for 20% above your target volume to account for any surprise deliverability issues!

Embrace Email Warm-Up

Before you get started on your cold outbound sales, you should properly warm-up your new, non-primary domains. Every ESP has its own spam filters, but a red flag for all ESPs is an account starts sending a ton of emails out of the blue. 

Start small (10-20 emails per day) and gradually increase the volume of emails sent over the course of 2-4 weeks to no more than 50 per day per Inbox. This allows service providers to recognize and trust your sending patterns. Using services like Instantly can automate this process, ensuring it's done systematically and is optimized for the best results.

Set Up Your DNS Records

Once you set up your domains, you'll need to ensure that your DNS records are configured appropriately for healthy email sending. MX, SPF, DKIM & DMARC are DNS settings that tell ESPs that you're a legit sender from a legit domain.

MX records are a type of DNS record that details the mail server responsible for accepting email messages on behalf of a domain. If anyone sends you an email, the MX records make sure it lands in the right server's inbox. You can have several MX records for backup to make sure no email gets lost even if one server has issues.

SPF (Sender Policy Framework) helps you list all the mail servers that are allowed to send emails on your domain’s behalf. Think of it as a guest list: when an email reaches its destination, the receiving server checks this list. If the email comes from a server not on the list, it’s like someone crashing the party — the email fails SPF and is treated with suspicion.

DKIM (DomainKeys Identified Mail) is like giving your email a special stamp of approval. When you send an email, DKIM adds a digital signature that is uniquely linked to your domain. This signature is hidden in the email's header and is verified on the other end using a public key that you’ve put in your DNS records. If the signature checks out, it proves the email really did come from you and hasn’t been tampered with along the way. (If you want to verify your DKIM record, here's a good tool).

DMARC stands for Domain-based Message Authentication, Reporting, and Conformance. DMARC is a bouncer for your email domain. It checks if the emails claiming to be from your domain are actually from you, using SPF and DKIM. If an email doesn't pass the check, DMARC can tell email servers to either sideline it or kick it out entirely. Plus, it sends back reports on anyone who's trying to impersonate you (tip: use ChatGPT to help you interpret these reports).

Set Up a Custom Tracking Domain

Setting up a custom tracking domain is essential for outbound email. Cold emails often include an invisible pixel that fires when the email is opened, helping track these rates. When tracking open rates, a rate above 35% typically indicates that your emails are reaching the inbox.

However, it’s crucial to use a custom tracking domain rather than a public one. Public domains can negatively impact your deliverability because they might be blacklisted due to misuse by others, potentially harming your reputation. Platforms like Instantly and Smartlead offer guides on setting up your own domain through a CNAME in your domain settings, allowing you to maintain an independent reputation.

One word of caution: open rate data from pixels can be inflated by email apps that preload emails, which might not reflect actual engagement. Once you confirm your emails are being effectively delivered, consider disabling open tracking to avoid being marked as promotional or spam, which can affect your campaign’s success.

Get Your Message Right

The content of your emails plays a significant role in campaign success. Crafting engaging, relevant, and actionable content that resonates with your audience can dramatically improve open and click-through rates.

Subject lines should be representative of what's in the body of your email - and the message should be relevant to the recipient with a clear call to action. Personalization can go a long way in driving engagement, but be cautious when using merge tags. Sometimes databases aren't up to date, and writing something like "I saw you're {Title} at {Company}" can make you an outbound laughingstock if it's not accurate.

You'll also want to vary your language and email structure with each new campaign so as not get fingerprinted by ESPs and tagged as spam. Spintax can be a great way to change up your message at scale, as it allows you to create several versions of the same message by replacing words and/or phrases with synonyms or other similar terms. Each email will use a different variation of that message.

For example, an email sign off using spintax might look like this:

Looking forward to {{Random|hearing from you|your thoughts}}!

One last tip: avoid words that look like spam, such as "reply now" or "incredible deal". If you're not sure if your message is spammy, you can check it here.

The Importance of Testing and Analytics

Continuous testing and refinement based on analytics are key to improving email deliverability. Remember that your audience may not want to receive the same email that you want to receive. And, outbound trends change quickly and frequently, so what worked 6 months ago may not work today.

Regularly conducting A/B tests on various elements of your emails, including layout, content, and sending time, can provide valuable insights that inform smarter, more effective email strategies - and can keep your own bias out of the equation.

Clean Your Lists

Effective list management is fundamental to maintaining high deliverability. Cold emails that bounce and invalid email addresses will hurt your deliverability efforts as well as your domain reputation.

While databases like Apollo and Cognism can help you get a segmented list of your target buyers, the data is never 100% accurate. You must regularly clean your list of inactive/unengaged subscribers and double check emails using a tool like NeverBounce.

Provide an Opt-Out Method

In some regions, such as California, it's required by law to include an option to unsubscribe in cold emails. Unsubscribe links are an easy way of achieving this, as a re softer opt-out methods like “If this isn't relevant to you, let me know and I'll get out of your inbox.”

Shut Down Bad Campaigns Quickly

If you notice that your open rates have tanked, people are opting out, and no one seems to be interested in your offer, turn off your campaign.

Take a look at your copy, send a few internal test emails to see where the message is landing, and evaluate your campaign approach. Continuing to run a bad campaign is worse than running no campaign!

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