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11 Secret Ways Of Improving Email Deliverability

by Nedim Talovic · Updated 20 Feb 2022}}

Many companies are struggling with email deliverability. That's why I'll show you different ways to deliver your marketing emails directly to the inbox. 

You've probably come across email marketing software claiming that they will handle email delivery for you. They won't because they can't. There are things that you should do, no matter what email marketing software you're using.

For example, did you know that you should buy a dedicated IP address if you send more than 50k emails a week or that there are some words that you shouldn’t use in your subject lines? If not, no worries, that's exactly what you can learn in this blog post.

In short, here is what you need to do:

  • Buy a dedicated IP address
  • Clean your list
  • Create a subdomain
  • Avoid buying email lists
  • Handle unsubscribers
  • Authenticate emails properly
  • Use feedback loops
  • Avoid spammy words in subject lines and content
  • Check your reputation
  • Check blacklists
  • Monitor deliverability

Let’s break this down.

#1 Buy a dedicated IP address

You probably use professional email marketing apps, but the trick is that most of them use shared IPs to send your newsletters. Of course, they’ll fight against spam as much as they can, and they mostly do that successfully.

However, when you send a large number of emails, you should consider buying a dedicated IP address. Having a dedicated IP reserved only for you means that nobody can harm your reputation (except yourself), and you don’t need to worry if some email provider will make some mistakes with handling the spam (low chances).

Mailgun suggests you use a dedicated IP address if you’re sending more than 50,000 emails per week, to isolate your reputation. They charge $59 a month for adding a dedicated IP. When to use a dedicated IP address

Another Mailgun competitor - SparkPost - will charge you $20 per dedicated IP address, but you can’t mix a free plan with a dedicated IP address.

SparkPost suggests that when you buy a new IP address, you should always methodically increase campaign volumes. Week by week.

Recommended thresholds

You can’t send millions of emails from a new IP address. In simple terms, ISPs always view email from new IPs as suspicious until they establish a positive sending reputation.

Warm-ups Matters

The left graph above shows what happens when you quickly warm up a new IP address. Being patient is a critical moment.

#2 Clean your list

Sometimes you should consider cleaning the list you have. Firstly, you can use commercial apps that remove emails that likely don’t exist.

These services charge by the number of emails you have, so if you have lots of subscribers, it means that you make enough revenue to pay it.

The problem might be not having an efficient anti-spam filter (CAPTCHA), which can result in getting non-existing emails.


Honestly, I have never used reCAPTCHA when asking for new subscribers because I think it may slow the growth rate, but if you collect too many spammy emails, then you should consider implementing this feature. 

Some sites require confirming the subscription by sending a confirmation email. I wouldn’t recommend you this since this may slow the growth rate.

Newsletter confirm

Source: WonderPlugin I haven’t tried this tool since it may also slow the process of acquiring new emails. But again, if I get in trouble with deliverability, I’ll give it a shot.

Another option is removing subscribers who don’t engage with your newsletters. Here’s what you can do. Send one of the following offers to those subscribers:

  • eBook
  • Webinar
  • Trial

If you send three newsletters in a few weeks and those subscribers don’t even open a newsletter, they are probably not interested. 

Furthermore, you can retarget those subscribers using Facebook Ads and Google Ads and check if these two services will match emails.

#3 Create a subdomain

You probably receive lots of newsletters that are not mailed and signed by domain. Instead, they’re mailed and signed by a subdomain.

I received a message from DigitalOcean where they tell me that I forgot to pay, and there’s an outstanding balance on my account. No worries, I’ll pay it today.

DigitalOcean Subdomain

As you can see, the message is mailed by and signed by

This is the best practice. When someone sends thousands of newsletters to a purchased list, using a subdomain will make sure that a potential damage is less for people. The email above isn’t a newsletter - it’s a billing notice. 

Here’s another example that shows how DigitalOcean sends emails signed by another subdomain reserved only for newsletters.

Mailed by and Signed by

You can see that there’s an unsubscribe link which is also a great practice. I don’t have to mention that an unsubscribe link is also available in the newsletter footer. 

With this practice, you’ll also help providers such as Gmail to classify your emails to know which emails are transactional and which are promotional.

#4 Avoid buying email lists

The golden rule of email marketing is to avoid buying lists due to an array of reasons. 

Firstly, it’s forbidden by the law (CAN-SPAM ACT). You are not allowed to send newsletters to people who haven’t give tou persmission. Every email in violation is subject to the CAN-SPAM ACT. Penalties can go up to $16,000, so non-compliance can be costly.


Secondly, you must know that there will be lots of fake (non-existing) emails. Businesses and domains stop existing over time. 

It’s a fact that 8 out of 10 businesses will fail within the first 18 months. In other words, your bounce rate will be above the average, so you can be blacklisted, and you won’t be able to send emails to people who subscribed. 

Now, don’t even think that setting a new subdomain will save you of being penalized. That’s simply not true.

#5 Handle unsubscribers

Whenever someone unsubscribes, you should remove him from the list. Why? Because when a subscriber doesn’t want to receive newsletters anymore, he can report your newsletter as a spam which can lead to spam filtering or blacklisting.

According to Convince and Convert, 21% of email recipients report email as spam, even if they know it isn’t. The same source says that 43% of email recipients click the Spam button based on the email “from” name or email address.

Now imagine how much of them will report your newsletter as spam when you don’t allow them to unsubscribe? I reckon at least 50%. CAN-SPAM ACT forces you to process opt-out requests for at least 30 days.

You must honor a recipient’s opt-out requests within 10 business days. You should always use an unsubscription link in the footer and let people unsubscribe if they want.

Make opting out as easy as possible - without charging a fee, requiring personally identifying information, or make the recipient take any step other than sending a reply email or visiting a single page on your site as a condition for honoring an opt-out request.

Unsubscribe me from the list

This example came from a newsletter I received from DigitalOcean.

Finally, you can’t sell or transfer the email addresses of people who tell you that they don’t want to receive more messages from you.

#6 Authenticate emails properly

Every month I receive an email from a bank that sends me a monthly statement. However, I noticed that the bank doesn't have authenticated messages. The photo above shows that.

Gmail couldn't verify sent message

Gmail couldn’t verify that … actually sent this message (and not a spammer).

When you see such a message, what do you usually think? Probably that the bank isn’t serious and doesn’t care about Internet security. In fact, they sent me a special SMS and online banking offer.

The reason why the message appears is that emails from my bank aren’t authenticated. If you’re not sure if your emails are authenticated and you don’t use Gmail, for example, you should search for “Authentication-Results” headers in email clients like Thunderbird.

Also, if the message is authenticated then there must be SPF or DKIM records. (spf=pass or dkim=pass) which are actually types of authentication.

#7 Use feedback loops

I already mentioned that you should make it easy to unsubscribe from the list to those who aren’t interested in your newsletters anymore.

The main reason is that when someone clicks on the Report Spam link in Gmail, or an equivalent link or button in other email providers such as Zoho, Outlook, or Yahoo, it will affect campaign deliverability.

Report Spam

Clicks on these anti-spam links are considered complaints. A feedback loop is a service that is provided by ISP's to original senders, so they know how spammy their campaigns are.

The major ISP providers send a feedback loop. Here is the list:

  • Gmail
  • Zoho
  • Yahoo!
  • Outlook
  • Yandex
  • AOL

Once you get a complaint, you should remove a subscriber from the list since it’s obvious that he’s not interested in your emails. 

If you continue sending emails to those subscribers and your deliverability rate will be lower. 
Most email marketing apps leverage feedback loops to protect their reputation.

If you have your custom solution and you haven’t implemented this yet, you should do it today.

#8 Avoid spammy words in subject lines and content

Using certain words in subject lines and the content could be a reason for going to the spam folder. Here’s the list of some words that you should avoid in subject lines:

  • $$$
  • 100% free
  • Act Now
  • Affordable
  • Cheap
  • Credit
  • Earn
  • Free gift
  • Income from home
  • Leave
  • Order now
  • Remove
  • Save $
  • Weight loss

The full list is available on Mequoda.

While magnet words help a lot, using the words above might complicate your life, and you don’t need that.

When I notice spam messages, I usually see words related to money. This photo above shows some of these words:

  • Earn money
  • Make money
  • Expect to earn
  • Double your
  • Extra cash
  • Extra income
  • Insurance
  • Guarantee
  • Earn per week
  • Million dollars

Simply said, avoid these words, and everything will be fine unless you have a reputation as big tech companies do.

#9 Check your reputation

Boosting your reputation will lead to improving the deliverability of your campaigns without questioning. One of the useful tools where you can check your reputation is Reputation Authority.

For example, when I enter an IP address, I can see that we don’t have viruses or spam. Also, we’re not suspicious, and so on. Our reputation score is 50/100 which means we’re neutral. That’s good since our domain is existing just more than a year.

Site with a reputation

But, if you check a spammy IP address, here’s what you can see. The reputation score is on the highest level - 100/100. In this case, less is better.

Low reputation site

Furthermore, the Spam score is 100%. Another great tool is where you can check if some IP has a poor email reputation or not. Here’s how it looks when you have a poor email reputation.

Bad reputation site

Another interesting metric comes from Return Path - Sender Score. Sender Score is on a scale of 0 to 100, and the highest score is the best score. If you check for, you’ll see that their Sender Score is 97 of 100.

Sender Score

Having Sending Score 97 of 100 is extremely well. Also, it’s interesting that you can see recent campaigns by Moz.

#10 Check blacklists

When IP or a domain get blacklisted, it’s not the end of the world although you might consider buying a new domain.

There’s one good and two bad news. The good news is that you can be whitelisted again, and the bad news are that it takes some time, and there isn’t only one blacklist.

There are many blacklists but most ISP's use Spamhaus, so being whitelisted on Spamhaus is very important. The Spamhaus Project is an international non-profit organization that tracks spam and related cyber threats.

Here, I’ll show you how to check if your IP/domain has been blacklisted. Firstly, open Blocklist Removal Center, and enter your IP address or a Domain name. After that, you’ll see something like on the photo below.


Jellymetrics’ IP is not listed in the database, but let’s see what to do when you get blacklisted.

Blacklisted IP Address

The first step is to identify what might cause the blacklist (bounces, spam complaints, authentication, etc). Once you identify what caused blacklisting, you can send a removal request, but before that make sure that the issue that caused blacklisting never happens again.

Policy block list IP removal form

I told you that The Spamhaus Project is the most important blacklist, but there are as well. Blacklists such as SURBL, URIBL, SORBS, and so on.

#11 Monitor deliverability

Achieving great deliverability is only possible with - monitoring deliverability. It’s well-known that most email sent is spam, but most delivered isn’t.

Most email sent is spam

Having a low sender score says that your delivery rate will be almost non-existing. Here are some common reasons why emails bounce:

  • Email address doesn’t exist
  • Domain doesn’t exist
  • Mail server won’t accept emails
  • No more space on the email account
  • The server is currently down
  • Too large message

When a hard bounce happens, you should immediately add those subscribers to a suppression list.

Hard Bounces vs Soft Bounces

On the other side, soft bounces deserve another chance because sometimes a server may be down, and also, the sender's server will try again to deliver a message within 72 hours.

For the reasons mentioned above, monitoring your delivery is very important. You don’t want to unsubscribe a guy who has no more space on your email account at the moment because he might be available again tomorrow. Maybe he becomes your best customer, who knows?


Having bad deliverability means that your efforts in collecting new subscribers are useless. Luckily, you could see here diffeernt ways of improving your email deliverability. 

If you’re experiencing deliverability issues, I’d always recommend you to start from your list. Again, never buy lists, but if you did, just drop it. 

Next, you should clean your list and remove people who are not interested in your business. 

Also, never forget to handle unsubscribers and using feedback loops since it tells you who’s reporting your emails as spam. 

Finally, monitoring delivery is key because every time incidents happen, you can fix them.