The Guide to Email Deliverability

March 29, 2022
 min read

What is email deliverability? It might not be glamorous, but it’s the foundation of successful outbound sales. If you aren’t prioritizing deliverability best practices you might end up throwing marketing money down the drain, sending emails into the void, or worst of all – getting your domain blacklisted.

You might have the most captivating and delightful sales email in the world, but if your emails are getting flagged as spam, they might never see the light of day.

To avoid your content withering away in the junk bin, here are some best practices we recommend following at – from list cleansing to the content itself. 

1.     Cleansing your lead lists BEFORE importing/ starting to send

If you’re purchasing contact lists from third parties, or even using a list of old leads from your CRM, it’s always best practice to run all the email addresses through a tool that verifies they’re still active.

People leave jobs all the time  and if you use bad email addresses, you can get flagged at an entire organization.

How to avoid: use tools such as Neverbounce, or Million Verifier to make sure the emails you have are good to go! 

2.     No attachments, and wait to include links

While it can be tempting to include more helpful information about your product or company in an attachment, most organizations have trained their employees to avoid clicking on links from unknown senders as it’sa potential phishing risk.

On top of that, some company spam filters will flag an email as potential spam just for including attachments.  

Best practice: if you have to include more content, it’s best to include it as a link and we recommend waiting until at least email 3 or 4.

Bonus tip: If you’re worried about sending links, use a CTA (call to action) that asks your prospect if they’d like additional content sent over as a link. 

Example: Would it be okay if I shared a link to a customer story on how they saved 10 hours a week writing sales content?

3.     Craft emails that look like they came from a friend

When creating content, don’t use templates, industry buzzwords, or long- winded product descriptions from your website. The goal is to make sure your content looks like it was written by a human and even better if it’s  in your voice!

Using popular sales templates or industry jargon is going to seem insincere and perhaps even lazy. It’s all about easily replicable frameworks.

People can tell if you took the time to write your own content and made it relevant to their industry or profession. If you have a few minutes, do a bit of research to add personalization about your prospect or their company - the extra effort will show.

Bonus tip: Try reading your emails out loud – do they sound like a sales pitch or an email from a friend?

4.     Avoid spam phrases and ALL CAPS SUBJECT LINES!!!

Spam filters are trained to look for common spam phrases (free, buy now, etc.), especially in an email’s subject line.

One resource at that we like to refer customers to is HubSpot's The Ultimate List of 394 Email Spam Trigger Words to Avoid in 2021 for a list of email spam trigger words.

In addition, don’t use more than two exclamation points in a row or use all caps in your subject line or email body.  Not only will your tone be off-putting, you’re also likely to get flagged as spam. 

5.     Update your content regularly 

At, we recommend regularly reviewing and refreshing your emails every 60-90 days.

Not only does this help you gather more data on which content is resonating with your prospective customers, but it helps you to avoid sending reused content to the same organization over and over again, which can also get you flagged as spam.

Bonus Tip: block off time on your calendar once a quarter to refresh your sales content.

If you’re a customer, ask your CSM about scheduling a quarterly content strategy session to review content and generate ideas for enhancing it. 

6.     Include unsubscribe links 

Do you really need to include an unsubscribe link? Yes.

According to the FTC's CAN-SPAM Act, companies are required to "include a clear and conspicuous explanation of how the recipient can opt out of getting email from you in the future."

Opt-out or unsubscribe links make it easy.

Not only is it polite and a requirement for larger companies to comply with CAN-SPAM & EUROPE, but if you don’t include one, the only option for customers is to reply directly to you to ask to be opted out, which will impact the accuracy of your reply rates.

7.     Images, videos, and GIFs, oh my!

If you want to try sending images or GIFs as part of your email campaigns, make sure to maintain a good text-to-image ratio (for example, don’t use huge images or an overwhelming number of images).

It’s also best practice to wait until the second or third email to send images/ GIFs to make sure your emails are getting delivered.  

Don’t use video, Flash, or JavaScript within your email.

Don’t embed forms in your emails.

8.     Regularly check your domain health 

Your company should be checking on your domain health monthly and pay attention to how it’s trending over time.

Tools: You can check the health score of your domain using free tools such as MX Toolbox or Mail Tester. If your company uses Gmail, you can also use Google Postmaster Tools to monitor your sending reputation.  

If you notice that your score has been decreasing, it’s important to do a content and process audit to determine what may have impacted your score and why. 

Bonus Tip: Positive responses can help boost your inbox placement, so in the event that your score dips, send some emails to internal users - both company and personal emails if possible - and have them send a response in the affirmative (ex: "Nice to hear from you! Yes" or even just "Yes!")

If you have a brand new domain, be sure to “warm up” your new inbox before you start sending any prospecting emails. To do this, you can use tools such as Warmup Inbox or MailReach.

9. Pay attention to throttle limits

Depending on which tool you’re using to send emails, be sure to follow their recommendations for email throttle limits (emails that can be sent during a particular period of time).

For example:

1.  Outreach recommends configuring Org-Level email limits. Outreach has a sending limit of 5,000 emails per week (or 1,000 emails per day). 

2.  Salesloft recommends setting the daily send limit to 250, although settings can accommodate allowing users to send up to 1,000 emails each day.

3.  HubSpot daily send limits will depend on the type of email provider and your HubSpot subscription type.

Bonus Tip: If you’re seeing issues with deliverability you should temporarily decrease your daily send limits. 

10. Consider creating a custom tracking domain

Custom tracking domains ensure that your links in the body of emails are wrapped with your tracking domain. This avoids third party links, which can cause spam filters to flag your email.

To set up a custom tracking domain for your team, follow these steps: 

1.      Decide which subdomain you would like to use. The format for subdomains follows this pattern: "".

2.      Once you’ve chosen your subdomain, contact the support center for your sales engagement platform so their support agents can set up the custom tracking domain. 

3.      Support will provide you with a CNAME reference using the subdomain you choose. 

4.      After you have your CNAME, reach out to your IT team or administrator to add the CNAME reference to your DNS record. 

5.      Once your DNS record is updated, inform the support team. Support will add the subdomain into your sales engagement platform. 

6.      Send emails with your own domain to drastically decrease the potential of your messages going to spam. 

Additional Resources:


· Outreach Deliverability Best Practices

· Outreach Email Best Practices: Avoiding Spam Filters

· Outreach: How To Enable the Custom Unsubscribe Link

· Outreach: How To Customize the Unsubscribe Signature Link


· Salesloft Email Deliverability Best Practices

· Salesloft Email Deliverability Webinar Recording

· Salesloft: Global Opt-Out

· Salesloft Email Deliverability Best Practices


· Improve email deliverability

· The Ultimate List of 394 Email Spam Trigger Words to Avoid in 2021

· HubSpot Sending limits for connected email accounts

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