Improving Deliverability for your Email Campaigns

Deliverability is key when it comes to a successful email campaign. It refers to the percentage rate of emails delivered to the inbox versus the total emails sent. With improved email deliverability, your email marketing campaign will have a higher ROI, or return on investment, which is the cost of sending the emails divided by the number of clients who responded.

Email deliverability is a very dynamic part of email marketing, as there is never one solution, and no guarantees of scoring a high success rate. In fact, it can even be a problem with major franchises. According to a study in the Journal of Direct, Data and Digital Marketing Practice, a whopping one-third of major companies had their emails flagged as spam. By setting aside the time and effort to understand the complex nature of deliverability, you’ll find yourself well on your way to crafting a top-notch email campaign.

If you are an email marketer, just starting out, you might wonder why any of this is relevant. I mean, you’ve been sending emails out to your friends and family for years, and so how could an email campaign be any different. Well, it is, and it’s strikingly different. When it comes to email campaigns, even the most legitimate of emails can find themselves ending up being blocked or sent to the spam folder by ISP’s. However, whether it’s subscribers that alert you to the issue, or test emails, there are ways around this problem.

In the following article, I’ll do my best to explain why this happens and what you can to solve it by introducing you to email authentication and how engagement and reputation affect your deliverability.

How Authentication Impacts Your Emails Deliverability

Let’s face it, spammers want to get their emails into your inbox. One of the ways they do this is to use multiple IP addresses. Fortunately for you, your mailbox provider is wise to this trick and will assess the sender’s authentication, as well as how long the IP address has been active, when it comes to deciding what to let through the gateway, and what not to.

An authenticated email means that the email is from the individual, group or organization that has actually sent it. In other words, it’s a verification technique, verifying that the domain in the sender’s address is in fact, that sender. The protocols used by ISP’s are in place to protect you from scams such as phishing. If your ISP cannot be certain the sender is on the up and up through these protocols, the email will be filtered. So, if you have authentication issues, your email campaign will not be as successful as you’d like. In order to get a good idea of what goes into email authentication, we can start with the basics: Sender Policy Framework, Sender ID, DKIM, and DMARC.

Sender Policy Framework or SPF

SPF checks the HELO identity of the server that sent the message, as well as the MAIL FROM section, which represents the sender’s email address. When you send emails in your campaign, each email that enters the recipient’s box will check the IP address to make certain it is permitted to send emails on your behalf.

Sender ID

When you send emails in your campaign, Sender ID will use an algorithm, known as the Purported Responsible Address, or PRA, which will take a look at the content, concentrating on the ‘From Address’ that your clients see. While Sender ID is not as prevalent as it once was, some ISP still uses it.

DomainKeys Identified Mail, or DKIM

DKIM creates both a public and a private key. The public key is found in the DNS, and the private key is accessible to the mail server. This means that when you send out your campaign emails, the header will contain a private key for the ISP to verify. DKIM also ensures that your email was not hijacked while in transit and edited before it hit the inbox.

In summary, when your campaign email encounters its destination, the inbound server will attempt to determine the source of the sender. The inbound server will test to see if the email is indeed, from who it claims to be from. So, a good way to make sure that your emails can pass this hurdle, do not send them from a free webmail address. Instead, use your own domain email address. Here, you’ll be able to manage your DKIM.

To manage your own DKIM is effort well spent when trying to increase your email deliverability. DKIM authentication is a way for you to have greater control over the authentication process. This means that the recipient’s mailbox will not see your emails as phishing or spam campaigns. As suggested earlier, you’ll want to send your campaign emails out from your own, personal domain email address. The process should be straightforward, with little variation between providers. This means that you’ll simply access your account settings, click on authenticate email, and then start the process.

Domain Message Authentication Reporting and Conformance, or DMARC

DMARC is designed to protect you from scams such as phishing, and compliments both DKIM and SPF protocols. Here, both the Marketer and Recipient are protected. Mailbox providers such as Gmail, Hotmail, and Yahoo require that all emails comply with the DMARC protocols. DMARC is valuable when it comes to protecting your reputation when spammers use your domain to send out junk mail. When you have DMARC and SPF authentication watching your back, your emails will be authenticated, and your deliverability ensured. Email authentication matters, as a marketer, it protects your reputation and your brand, while enhancing deliverability.

Engagement and Reputation

Engagement refers to how your recipients engage with your emails. Did you know that ISP’s construct a profile based on how recipients react to your emails? Well, they do, and it’s for this reason that you only send emails which are ones your recipients will find engaging. To do this, always check on your bounce rate, open rate, and spam rate, as well as removing invalid email addresses from your list, as well as removing any from the content of your email.

If your recipient opens the email, replies moves it to a folder or adds you to an address book, your ISP will view these as all good signs, and hence add to your reputation. A low bounce rate of under 5 percent and a spam rate of 0.1 percent or less is also a good indicator of healthy engagement.

However, if the recipient deletes the email prior to even opening it means that they could care less, so absolutely no engagement exists. If they mark it as spam, it also is a sign that no engagement exists. You also want to check your domain and IP reputation against blacklists. You can do this quite easily by using this free Blacklist check tool:


There’s no one formula to calculate a sender’s reputation. In fact, mailbox providers usually use their own reputation filters. In general, a reputation based filter examines each incoming email, performing it’s very own threat assessment, and checks for complaints against the sender, content, spam traps, blacklists, and the overall volume of emails.

Online Tools to Check Sender Reputation

There are some tools available to you to do random checks on your reputation as a sender. In doing random checks, you’ll get a good idea of how solid your reputation is, and if it is not, then you are alerted to the problem and can look for a fix. In general the higher your score, the better your email deliverability rate.







Know Your Spam Filters

Return Path controls approximately 70 percent of the whitelist market and is the undisputed global leader when it comes to email deliverability. They do this by their intuitive attempts at spam management, which works by verifying emails from reputable sender’s based on a scoring system. This scoring system allows Return Path to whitelist, verified, reputable senders. Return Path also provides email campaigners a variety of services to assist them in improving their marketing stats.

There’s no doubt about it, the success of your email campaign depends on the knowledge you have regarding the role filter technology plays in your endeavors. So, it’s crucial to know how your spam filter works, and understand how your email service utilizes them.

When it comes to authentication, it was your inbound server making the decision as to whether the email was from an authenticated sender. Here with your spam filters, it’s all about content. Email accounts will have spam filters which will examine your email content as a whole, judging it on its own criteria. If your content happens to meet the criteria, your email gets sent to the spam folder. Such criteria can include:


  • Repeated use of the dollar symbol: “$”
  • The message typed all in Caps
  • Large areas of unused space, frequent unnecessary spacing
  • Large bold font sizes or irregular font sizes
  • Consistent use of misspelled words
  • Spammy subject lines which portray scam activities
  • Poor grammar and punctuation
  • The email contains links from blocked domains
  • Dead/inactive links


For good examples, just go to your own spam folder, and take a look at the content of these emails. Chances are good, that they will all be about earning the most amount of cash in the least amount of time, trying to get you into a pyramid scheme or business scam. From reading these, you can get a good idea of the criteria used.

How to Check Campaign Emails for Spammy Content

When it comes to your content, remember to keep it useful to increase deliverability. Avoid messages that make exaggerated claims, are manipulative, pushy, or cheap. To give you a basic idea, check this small sample of trigger words to help you keep your email out of the spam folder:

  • 100% free
  • 50% off
  • Bargain
  • F r e e
  • Fast cash
  • Please read
  • Prize
  • Satisfaction guaranteed
  • We hate spam
  • Click here!
  • Offer Expires!

If you are new to email marketing, and still concerned about content, there are a host of free, online services where you can paste your content, and receive a report. These sites include:

  • MailTester
  • EmailOnAcid
  • Litmus
  • PostMark
  • Isnotspam

If You Find Out You Were Blocked

If you’ve discovered that you’ve been blocked by an ISP, contact that ISP and see if you can get yourself removed from the blocked list. To do this, take a look at your delivery reports to find out which ISP blocked you. Next, hit up the ISP’s site and follow the steps to get yourself removed. Whatever information the ISP asks for, just give them.

Permission Based Email Lists Enhance Deliverability

Having a permission-based email list can increase email deliverability, which can then lead to an increase in sales and productivity. With a permission-based email list, you have clients who have given you permission to receive your campaign emails. Permission can be granted directly, by the individual subscribing or adding their email to your list, or by already in a relationship with that business, individual or organization.

By sending your emails to those who have given you either implied or direct permission, your open and click-through rates can reach 30 to 40 percent. As you can see, sending emails to those on a permission basis, means that you’ll also have a much higher ROI for your efforts:

How does this type of list affect your deliverability rates? Simple. Email campaigns built on the foundation of permission means that your emails will not be seen as spam. Remember email providers want to protect their users, so pay close attention to complaints and emails marked as spam. Once their email providers realize that your emails are marked as spam by recipients, they’ll automatically filter them to the spam folder.


As you can see, spam filters are an absolute necessity when it comes to preventing us from being in contact with spammers or phishers. We need these filters, which makes it all the more crucial for email marketers to know exactly how they work, and use them to their advantage. By knowing how filters work, how to control their authentication, as well as how content affects your engagement and reputation, email marketers can ensure that their message can pass through the gateways, and find themselves in their client’s inbox, where they belong.


Need help with your email marketing and SEO efforts? Get in touch today to find out how we might be able to help!


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Craig Campbell

I am a Glasgow based SEO expert who has been doing SEO for 18 years.

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