In general terms, email deliverability is the likelihood of your email reaching the recipient’s INBOX.

Naturally, you would ask – where else would it go? So here’s a fun fact – on an average 45% of all emails are landing in SPAM.

Table of contents
1. An email’s journey to the inbox

1.1 Hurdle #1 -Validity of recipient’s email address
1.2 Hurdle #2 – Technical problems at server
1.3 Hurdle #3 – Blocking by ISPs or email service providers
1.4 Hurdle #4 – The actual SPAM filter
2. Why is email deliverability important
2.1 Increase competition
2.2 The cost involved with email marketing
3. Finally, getting to the inbox
4. Simple tips to improve email deliverability

5. FAQs

An email’s journey to the inbox

It seems like a fraction of a second between the time an email leaves your browser and reaches your recipient’s inbox. But that email has crossed many hurdles within that split second.

Hurdle #1 -Validity of recipient’s email address

Did you send the email to a valid email address? If not, you will get a hard email bounce. This can be due to several reasons such as typos, wrong domain, etc.

However, this mostly happens with email addresses that are too old. They were valid and active at some point but are now closed.

This is more common with business email addresses than personal email ids. People quit their jobs, companies shut down, or sometimes just change domain names. In general, if you have a business email address that is more than two years old, it’s most likely no longer valid.

Hurdle #2 – Technical problems at the server

Let’s say you have a valid email address, then your email would be able to reach the ’email server’ of your recipient.

However, even then, certain technical issues can cause soft bounce.

It can happen for different reasons:

  • The recipient’s mailbox was full (the user exceeded their quota)
  • The email server was down
  • The message was too large for the recipient’s inbox
  • The server detected possible malware in your email
  • Certain attachments are not accepted by the server

From your side, you can only ensure that your email text and attached file are generally acceptable to email servers.

Hurdle #3 – Blocking by ISPs or email service providers

ISPs are “Internet Service Providers”. Previously, only companies such as AOL, Comcast, etc. were called ISP. However, the term is now widely used to include companies such as Google, Outlook, and Yahoo that provide email clients. They are more of an email service provider, but they are sometimes referred to as ISP.

These email service providers often market themselves for their ability to keep their customer’s inbox free of spam and fraudulent emails.

That’s why they check each email for –

  • Email Content – Filter out emails with content that appears spam, phishing, or fraudulent. It also looks for suspicious images and links that have been blacklisted by other users.
  • Sender’s email address and IP – if the sender’s email ID or IP address is marked by others for sending spam, it’s a red flag.
  • Customer’s preferences and previous spam records – if email recipients have marked certain types of emails (such as newsletters) as spam in the past.

This is a relatively tough hurdle for email marketers to clear. As the email marketing world gets more competitive, it will take even more work for marketers to differentiate themselves from other marketers marked as spam.

Hurdle #4 – The actual SPAM filter

Even if the email passes your ISP’s block, the recipient may have installed another SPAM filter to block certain types of email. People tend to block marketing and promotional emails when they receive them frequently.

So if you send too many emails to people who never open them, you run the very real risk of getting marked as SPAM and creating this hurdle for yourself.

But that's not all. If too many people mark your emails as SPAM, then the risk expands to Hurdle #3 level. In that case the ISPs will mark your email address and IP address as the origin of SPAM. Oops -you've just added another hurdle for yourself.

Finally, getting to the inbox

Only when all these hurdles are overcome will the email reach the inbox and be considered delivered.

For email marketers and sales teams who send cold emails, these hurdles can be difficult to overcome every time, considering the fact that – 45% of all emails are marked as SPAM.

Then you get a hang of how important the “email deliverability” factor is.

When you invest your marketing dollars and time in writing emails and building your prospect list, you naturally want to maximize your email deliverability. In other words, it maximizes the chances of your email reaching your inbox.

Why does email deliverability matters?

Email deliverability is one factor that clearly has a lot of importance for online marketers. But even still 45% of all emails are getting classified as SPAM.

high percentage of spam

This means a large number of marketing emails are landing in SPAM. So, the majority of email marketers are not able to do a key job – getting their emails to inboxes!

It’s definitely a problem if your email goes to SPAM instead of inbox. But let’s examine how big a deal it really is.

Increasing competition

The Internet is growing every day, reaching thousands of new people. Therefore, new businesses are getting into the online marketing game each day.

This chart indicates that online advertising costs are steadily rising. Even then, the total spend on online ads is steadily increasing.

That means, other online marketing channels – including email marketing -are also getting more expensive.

The costs involved with email marketing

Email marketing is a lot more than sending a pretty-looking HTML email to your prospects.

There is a lot of work that goes into – prospecting, list building, content generation, marketing automation, campaign tracking, and follow-up.

All those things cost time and money.

Prospecting and list building

If you buy your email list from a marketing agency (not recommended), the costs are obvious.

But even when you organically build your email marketing lists by capturing leads on your website, you are still spending considerable time and money to generate and promote content. Moreover, it can take a fair amount of time to build your list this way.

All in all, your email list comes at a considerable cost. So each email landing in spam is waste of those marketing dollars.

Content generation

Arguably, the means of content generation’ have been getting cheaper over time. We have so many inexpensive tools to help us – canva, vimeo, biteable etc.

But you must create high quality, differentiated content to stand out from the heavy competition. And that takes time and money.

Marketing software to automate and track campaigns

This part of the email marketing game may just work in your favor – if you’re careful.

Tools like Woodpecker,, Mailshake, Fuzen, GMass, Mailchimp have made it cheaper and easier to effectively manage campaigns. But because Fuzen leverages the powerful Google Drive to do most of the heavy lifting in email automation workflows, it presents lighter, user friendly and much cheaper alternative to mailshake or, GMass .

But you need to be smart in identifying your exact needs. Then select a tool best suited for those needs.

For example, if you are a B2C marketer sending 50,000 emails a day, you are better off with Mailchimp.

But if you are sending a couple of hundred emails to B2B prospects, you can use tools like “SafeMailer’s Email Automation” to make sure your email doesn’t get flagged as SPAM.

But all these tools cost money and time to set up and execute c

How to test email deliverability?

Considering how important email deliverability is to the success of your email campaigns, the need to regularly monitor email deliverability becomes quite obvious.

So how can you go about testing the deliverability of your emails? Which factors would need to be tested and do we have any tools available to test them?

Regularly monitor email opening rates

The simplest thing that you can (and must) do to check email deliverability is to regularly monitor the opening rates for your email campaigns.

Since we cannot track how many emails reach INBOX, the next best thing that we can measure is – how many emails are getting opened. Email outreach tools like safemailer, will provide you detailed analytics of how many emails are getting opened and who are opening them.


Track these numbers on regular basis to ensure they are steady. Stable opening rates will indicate that your email deliverability and sender reputation is also stable.

The moment you see any significant drop in email opening rates, you can use any of the following tools to check the deliverability and sender score of your emails.

Tools to check email deliverability

1. Mailtester

This is our favorite tool to check the deliverability and sender reputation for our email campaigns at SafeMailer.

Created by geeky email software engineers, it’s a cheap, simple, and efficient way to quickly test the quality of your newsletter.

MailTester will analyze your message, mail server & sending IP. It will then generate a detailed report of what’s configured properly and what’s not. Your result will be accessible for 7 days with the free version, or for 30 days if you choose a paid plan and create an account.

test email spammyness and deliverability with mailtester

If you occasionally perform manual tests, you can access their web-interface for free, without even creating an account.

2. SendForensics

They offer a free email deliverability test. You just need to sign up & add the unique email address provided by them to your mailing list for real time deliverability testing.

They first advise any correction of your sending infrastructure, then they check your content & give you a final score.

There is no limit to the number of email tests you can send to SendForensics to test, so it is not an issue to test every single campaign prior to launch to maximize the deliverability.

3. GlockApps

GlockApps is a email deliverability and spam test tool in one place.

It shows you delivery results in real-time for each seed list account. A seed list is a test ID and a list of email addresses across the top ISPs – Gmail, Hotmail, Outlook, Yahoo, AOL, and others.

You can see whether your email has landed in the Inbox, Spam folder, Promotional/Social tabs, or was never delivered.

GlockApps Bounce Monitor, a tool that tracks bounced emails & collects all the analytics, can be integrated with Amazon SES, SparkPost, SendGrid, and Mailgun.

4. Other tools – MX Toolbox, SpamCheck etc.

There are a few more tools which will help you check the technical aspects of deliverability of your emails. These may be useful when you are operating at scale and want to take care of all technical aspects of email deliverability and not just cold email automation.

Here’s a more detailed list of tools that you can use to test email deliverability for your email outreach campaigns.

Simple tips to improve email deliverability

  • Never buy a mailing lists. You don’t know of the quality or authenticity of these emails and you will end up with too many bounced emails.
  • Set up separate domain and email addresses for marketing purposes. You minimize the risk of damaging your main domain reputation, in case your emails get marked as spam.
  • Avoid sending bulk email blasts. They increase the chance of getting filtered by ISPs.
  • Invest more time and thought in writing emails that your audience will find interesting. Otherwise, what’s even the point of sending those emails anyway?
  • Take care to avoid certain spam trigger words and phrases in your email copy.

These tips can help you improve the deliverability of your emails. However, you will also need to test it on a regular basis to ensure it doesn’t slip.


Q. What factors affect email deliverability?

A: Several factors can affect email deliverability, including the content of the email, sender reputation, email authentication, email list hygiene, and subscriber engagement.

Q. What is a sender reputation, and how does it affect email deliverability?

A: A sender reputation is a score that internet service providers (ISPs) and email filters use to determine whether an email is spammy or not. The sender reputation is based on various factors, such as the email volume, bounce rate, spam complaints, and engagement rate. A good sender reputation can help improve email deliverability, while a poor reputation can cause emails to be marked as spam or blocked entirely.

Q. What should I do if my emails are not getting delivered to the inbox?

A: If your emails are not getting delivered to the inbox, you can check your sender reputation, email authentication, and email content to see if there are any issues. You can also contact your email service provider or the recipient’s email service provider to resolve any deliverability issues. Additionally, you can try segmenting your email list, improving your email content, and cleaning your email list to improve deliverability.

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