Cold Email Deliverability 101: The Ultimate Guide to Inbox Success

Looking to boost your email marketing efforts and increase your chances of reaching your target audience's inbox? Look no further! In this ultimate cold email deliverability guide, we will dive deep into the world of cold email deliverability. Mastering the art of getting your emails into the inbox can be a game-changer for businesses and individuals alike. Whether you're a salesperson looking to connect with potential clients or a marketer aiming to promote your latest product, understanding the factors that affect email deliverability is key.
August 1, 2023
Cold Email King

What is Cold Email

Cold Email with poor deliverability
Example of a Cold Email with poor deliverability...

In the world of online business, cold emailing is a bit like knocking on the doors of potential customers, collaborators, or mentors. 

It's a strategy used to initiate a conversation and build a relationship with someone who doesn't know you or your business yet. 

The term "cold" refers to the fact that you're reaching out without any prior contact or relationship with the prospect.

Let's use a practical example. 

Suppose you've just launched an agency that specializes in ecommerce marketing. You've got your site built, your blog up, your service ready, and are ready to accept new customers. 

So, how do you get the word out?

Here's where cold email outreach comes into play. You've identified some brands that you're able to help & you've built your list.

So you decide to send them a cold email, introducing yourself and your service.

A well-executed cold email has to accomplish several things:

Example of a successful Cold Email with good deliverability.
Example of a successful Cold Email with good deliverability.
  1. It has to capture attention, which starts with a compelling subject line.
  2. It must establish who you are and why you're reaching out.
  3. It should communicate the value you're offering (in this case, why your skateboard decks are unique).
  4. And importantly, it should have a clear call to action - what you want them to do after reading your email. This could be visiting your website, checking out your service, or agreeing for a call.

The video above summarizes everything you need to know about running a successful cold email outreach.

The keys, however, are scale, personalization, research and above all, deliverability. 

And deliverability is what we're going to be focusing on here. 

What type of results can you get with Cold Email?

Results from Cold Email Outreach

Cold Email is amongst one of the best low cost highly effective marketing strategies out there. 

It's amongst the few marketing strategies out there that don't require a huge upfront investment but instead a bit of technical knowledge on how sending, delivery, and copywriting work. 

The photo above showcases some of the results we've been able to generate using Cold Email Marketing over the past few months. 

This outreach was centered around generating calls for our Growth Hacking Course.

5.8k emails sent.

97 replies.

10 opportunities. (5 were not tracked)

All of this was made possible because WE UNDERSTAND COLD EMAIL DELIVERABILITY.

What is Cold Email Deliverability?

Example of Good Cold Email Deliverability
Example of Good Cold Email Deliverability

Imagine you've decided to throw a surprise birthday party for a friend. You create these awesome digital invites and send them out to all your friends via email. But here's the catch, what if some of those invites land in your friends' spam folder instead of their inbox, or even worse, they never reach your friends at all? 

That would certainly put a damper on your party planning, right?

Cold Email Deliverability is a bit like making sure all those digital invites land directly in your friends' inboxes, and not in their spam folders or elsewhere. In the context of business, it's about ensuring that your cold emails actually reach the inbox of the people you're trying to connect with.

Every email service provider, think Gmail or Yahoo, has these smart gatekeepers (spam filters) that decide whether your email is worthy of the inbox, or if it should go to the spam folder, or be blocked entirely. This decision is based on many things: your email content, your sending reputation, your email server's reputation, and whether your email looks like spam or not.

Improving cold email deliverability means that you're doing things to make sure those gatekeepers see your email as legit and deliver it to the inbox. 

This includes stuff like:

  1. Verifying your email: Ensuring your email is coming from a reliable source (domain), and not some sketchy place on the internet.
  2. Maintaining a good sending reputation: This means you're not sending tons of emails that bounce or get marked as spam. It's a bit like having a good credit score.
  3. Warming up your email: Just like you'd warm up before a run to avoid pulling a muscle, you gradually increase the number of emails you send if you're using a new email or domain. This helps build your reputation with the gatekeepers.

Why is this important for your online business? Just like ensuring your friends receive the party invites and attend the birthday bash, making sure your cold emails land in the right inbox increases the chances of your email being opened, read, and acted upon. It directly impacts the effectiveness of your cold email outreach, thereby helping you build connections, increase your brand visibility, and ultimately, drive more sales.

Consequences of Bad Cold Email Email Deliverability...

Bad Cold Email Deliverability

What repercussions can you expect from having suboptimal email deliverability? 

Here are several downsides to consider:

With emails failing to reach the inbox, recipients will be unable to open or read your messages.

Both new and existing customers might miss out on the latest updates, news, or promotions from your business.

Critical notifications, such as shipping information or password resets, may fail to get through to your customers.

Poor email delivery can negatively impact your business's bottom line, leading to a reduced return on investment (ROI) due to messages not reaching their intended recipients.

Your competition with superior email deliverability rates will have a greater presence in potential customers' inboxes, gaining a competitive edge.

The inability to deliver emails effectively will prevent you from tracking crucial performance indicators such as open and click-through rates.

How to Improve Cold Email Deliverability:


Example of Glockapps SPF & DKIM Report

These are authentication protocols that add a level of trust to your emails, signaling to ISPs (Internet Service Providers) that your emails are legitimate and not spam. 

SPF (Sender Policy Framework) verifies your email's source IP, DKIM (DomainKeys Identified Mail) ensures that your email content hasn't been tampered with in transit, and DMARC (Domain-based Message Authentication, Reporting, and Conformance) builds upon SPF and DKIM to improve email security.

2. Warming up for 2 Weeks: (Even 1 month if possible) 

Warmupinbox Warm Up Stats
Warmupinbox Warm Up Stats

If you're using a new email address or domain, you should 'warm it up' by gradually increasing your email volume over time. 

Start by sending a few emails on the first day, then slowly increase this number over a two-week period. 

This helps to build your reputation with ISPs and reduce the chance of your emails being marked as spam.

Domain age is a very critical factor for email deliverability.

A domain that's a year old will always outperform a domain that's a week old.

3. Purchasing Top Level Domains:

GoDaddy TLDs
GoDaddy TLDs

A top-level domain (TLD) like .com, .net, or .org can add credibility to your emails. It's best to avoid using less popular or unusual TLDs, as they can sometimes be associated with spam and can potentially harm your deliverability.

Additionally, ESPs know that spammers prefer Low Level Domains as they're cheaper, hence, why we recommend you stick to TLDs.

4. Cleaning Your List:

Email Cleaning Stats
Email Cleaning Stats

Maintaining a clean email list is crucial.

Before plugging your list into your Cold Email Outreach tool, make sure to clean it for bounces using tools like NeverBounce and others.

5. Spintax:

Example of Spintax
Example of Spintax

Spintax, or spin syntax, is a way of creating unique variations of text.

This can be useful in cold emailing to personalize your emails and avoid them looking like mass-produced copies, which could get flagged by spam filters.

6. Avoid Spam Triggering Content:

Example of Spam Content Detector
Example of Spam Content Detector

Certain words and phrases, excessive use of caps or exclamation marks, and too many links or images can trigger spam filters. Make sure your emails look and sound professional and avoid using spammy language.

7. Dedicated IP (IF POSSIBLE):

Using a dedicated IP address for sending emails means you're not sharing your IP with other senders. This is beneficial as it ensures your sender reputation is solely based on your actions and not affected by others who might be sending spam from the same IP.

Monitoring Your Cold Email Deliverability

Monitoring Overall Cold Email Deliverability
Monitoring Overall Cold Email Deliverability

Once you've done all of the above, it's time to begin monitoring your cold email outreach deliverability on a frequent basis. 

This can be done by: 

1. Track Bounce Rates:

8 Soft Bounces Tracked
8 Soft Bounces Tracked

Your bounce rate represents the percentage of emails that were not delivered. There are two types: hard bounces (permanent delivery issues like non-existent email addresses) and soft bounces (temporary delivery issues, such as full inboxes). 

Monitoring these rates helps identify problems in your email list or content that might be causing delivery issues.

2. Monitor Spam Complaints:

These are instances when recipients mark your emails as spam. Having a high number of spam complaints can severely damage your sender reputation, so it's crucial to keep an eye on this and try to keep it as low as possible.

3. Use Email Deliverability Tools:

Tools like GlockApps, Mail-Tester, and SendForensics can provide valuable insights into your email deliverability. These tools can help you test and monitor your emails' deliverability rates, analyze your email content, check your sender score, and more.

4. Review Open and Click-Through Rates:

Low open rates and click-through rates can be indicative of deliverability issues. If these rates are consistently low, it might mean that your emails are landing in spam folders or are being blocked by ISPs. 

You'll need to investigate the potential causes and take steps to improve these metrics.

It's also important to note that monitoring open & click through rates can be treated as a double edged sword. 

Whilst it does provide insights regarding what's happening with your emails, it also makes your emails more likely to hit spam as it necessitates the use of additional HTML code within your email copy. 

5. Check Blacklists:

IP Blacklists
IP Blacklists

If your emails are not getting through, it might be because your IP or domain has been blacklisted. There are tools like MX Toolbox that allow you to check if you're on any email blacklists.

6. Maintain a Healthy Sender Score:

Your Sender Score, calculated by ReturnPath, is like a credit score for your reputation as a sender. It ranges from 0 to 100, with higher scores indicating a healthier reputation. Keep an eye on your score to ensure that it stays high.

7. Regularly Test Email Deliverability:

Run deliverability tests to different ISPs regularly. This will allow you to catch any sudden drops in deliverability and take corrective action promptly.

8. Analyze Engagement Rates:

Track metrics like reply rates, conversion rates, and unsubscribe rates. These can give you an indication of how well your emails are being received and whether you're seeing a positive return on your efforts.

By diligently monitoring your email deliverability, you can quickly spot and rectify issues before they become significant problems. Remember, good deliverability is a cornerstone of effective cold email campaigns, so it's worth investing the time and effort to keep an eye on it.

9. Cleaning your list:

Last but not least, always bounce-check all your cold email outreach lists.

Tools like NeverBounce work by verifying the email addresses on your list, ensuring that they are valid and active. 

This helps to reduce the number of bounced emails, which is an essential aspect of email deliverability. 

A high bounce rate can hurt your sender reputation, leading to more of your emails being blocked or ending up in the spam folder.

Cold Email Limits & Cost:

Cold Email is cheaper than other marketing methods.
Cold Email is cheaper than other marketing methods.

As of recent, you'll find that the best practice for maintaining the longevity of GSuite & Outlook is to limit your sending to no more than 45 to 50 emails per day from a single inbox.

This implies that to send about 1000 emails daily, you'll need to use roughly 23 inboxes.

If you want to send out 5000 emails per day while adhering to these limits, you'll require 112 inboxes.

Given the average cost of an inbox is around $6 today, your monthly expenditure for sending out 5000 emails per day will be about $672, which equates to 150,000 emails per month.

Typically, 150,000 emails sent should yield around 150 positive responses, calls, or engagements.

This results in an average engagement cost of roughly $4.48, which is a significant saving compared to standard advertising costs.

Bear in mind, these limits and estimates might fluctuate, but they are the averages currently observed in the market.

Regarding the number of inboxes per domain, it's preferable to stick to a maximum of 3-4 inboxes for each domain.

The fewer inboxes you have, the better off you are.

These are the limits you should adhere to.

Maximizing your cold email outreach deliverability ensures that you're keeping your cost of engagement as low as possible. 

Things to avoid in terms of Cold Email Deliverability:

How to not end up in spam.
How to not end up in spam.

1. Ignoring Basic Deliverability Practices:

Do not neglect the fundamentals of email deliverability. This includes not using a professional email address, not creating engaging and personalized subject lines, and sending your emails at times when they're unlikely to be read.

2. Skipping SPF, DKIM, & DMARC:

These are essential protocols that authenticate your emails and show that they're not spam. Failing to use these can lead to your emails being blocked by ISPs or landing in spam folders.

3. Not Warming Up Your Domain or Inbox:

If you've just set up a new email address or domain, don't immediately start sending out hundreds of emails. This can be seen as spammy behavior and harm your sender reputation. Instead, start small and gradually increase your email volume over a period of at least two weeks.

4. Using Lower-Level Domains:

Avoid using less popular or unusual domains, as these can be associated with spam. Stick with top-level domains (TLDs) like .com, .org, or .net, which add credibility to your emails.

5. Neglecting List Hygiene:

If you're not regularly cleaning your email lists, you're risking your sender reputation. Ensure you remove hard bounces, unengaged subscribers, and anyone who has opted out of your emails.

6. Overlooking Spintax:

Not using spintax, or spin syntax, can make your emails look like mass-produced copies and get them flagged by spam filters. Use spintax to create unique variations of text and personalize your emails.

7. Including Spam-Triggering Content:

Ensure your emails don't contain elements that could trigger spam filters. This includes excessive use of caps or exclamation marks, too many links or images, and spammy language.

8. Sharing IP with Other Senders:

Sharing your IP address with other senders means that your sender reputation could be impacted by their actions. Avoid this by using a dedicated IP address for sending emails.

Remember, following these guidelines can significantly improve your cold email deliverability, and avoiding these common mistakes will ensure your emails reach the inboxes of your intended recipients.

Tools to use for Cold Email Deliverability:


MXToolBox Example
MXToolBox Example

MXToolBox is a widely-used, versatile online tool for monitoring various aspects of your domain's health, including email deliverability. Its primary function is to provide real-time monitoring and diagnostic services that can assist in identifying potential issues with your email servers. Here's how you can utilize MXToolBox to enhance and oversee your cold email deliverability:

1. Email Deliverability Monitoring:

MXToolBox's deliverability tool can help identify if your domain is on any of the most popular public blacklists, which can adversely affect your email deliverability. If you're blacklisted, your emails could land in the spam folder or be blocked entirely. By promptly detecting blacklisting, you can take necessary steps to get de-listed, thereby improving your email deliverability.

2. MX Record Checking:

MX (Mail Exchanger) records direct your emails to the servers you designated to handle your email traffic. MXToolBox can help ensure your MX records are set up correctly, which is crucial for email deliverability. Incorrect MX records could lead to email bounces or non-delivery of emails.

3. SPF, DKIM & DMARC Verification:

MXToolBox can check the validity and correctness of your SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance) records. These are essential email authentication methods that help prevent email spoofing and phishing, thereby increasing the likelihood of your emails being delivered to the inbox.

4. SMTP Diagnostics:

SMTP (Simple Mail Transfer Protocol) is the standard protocol for sending emails. MXToolBox offers a SMTP diagnostics tool that can identify potential issues with your SMTP server that might prevent emails from being delivered.

5. Continuous Monitoring:

With MXToolBox, you can set up continuous monitoring of your email servers. This allows you to get instant alerts when potential problems are detected, enabling you to address issues before they significantly impact your email deliverability.


Glockapps Example
Glockapps Example

GlockApps is a comprehensive deliverability suite used by email marketers and businesses to enhance and track their email deliverability. It offers a range of tools to test, analyze, and improve your email performance. 

Here's how you can use GlockApps to better your cold email deliverability:

1. Email Deliverability Testing:

GlockApps allows you to run deliverability tests to see where your email ends up - Inbox, Spam, or Updates, across different ISPs. By understanding where your emails land, you can then make the necessary adjustments to your campaigns to improve deliverability rates.

2. Spam Score Checking:

GlockApps provides a spam score by running your emails through common spam filters like SpamAssassin. It also provides recommendations on how to lower your spam score, which can improve your chances of avoiding the spam folder.

3. IP & Domain Reputation Checks:

With GlockApps, you can check the reputation of your sending IP and domain. If your IP or domain is blacklisted, your emails are more likely to be marked as spam or rejected, which is detrimental to deliverability.

4. Email Analytics:

GlockApps provides in-depth analytics about your email campaigns, including open rates, click rates, and bounce rates. Understanding these metrics can help you optimize your campaigns for higher engagement, which can in turn improve your deliverability.

5. DMARC Analytics and Reporting:

GlockApps can analyze your DMARC reports, providing actionable insights to improve your email authentication practices. Implementing DMARC effectively can significantly increase your email deliverability by protecting against email spoofing.

6. Bounce Tracking:

GlockApps can track and categorize your bounced emails, giving you insight into why emails are not being delivered. This can help you take corrective measures to reduce your bounce rate, enhancing your overall deliverability.

In a nutshell, GlockApps offers a set of robust tools that can significantly aid in improving and monitoring your cold email deliverability. It's a valuable aid in keeping your email campaigns optimized and ensuring your emails reach the recipient's inbox.

Growth Hacking Bootcamp on Cold Email Outreach

If you enjoyed this comprehensive guide, you'll also enjoy our Cold Email Outreach module in the Growth Hacking Bootcamp which explains EVERYTHING you need to know regarding successful cold email outreaches. 

We go over setup, copywriting, satelite domains, automation tools, and much more.

Join us: Growth Hacking Course

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