Email Deliverability and Subject Line


For 2022, Webbula is launching a series of blog posts about email deliverability topics. We have a variety of esteemed authors from the email industry lined up to participate. 

  • Subscriber Management: How to Start, Maintain, and Break Up by Elizabeth Jacobi. Read it. 
  • Email Opt-Ins: It's All About Consent In the End by Matthew Vernhout. Read it here. 
  • Email Authentication 101: What It Is And Why It Is Important For Brand Reputation by Yanna-Torry Aspraki. Read it here. 
  • Why Blocklists Make Us Better Email Marketers by Andrew Kordek. Read it
  • IP Warming - Do It Right or Do It Twice. Read it

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The Problem

The view that email Subject Lines have a major impact on deliverability has been
around for as long as I can remember - certainly the last 20 years.

It originated back in the early days of personal email and was an issue for a while. The inbox providers at the time, such as AOL and telcos like Comcast, suddenly found themselves dealing with an enormous number of spam emails. Worst of all, these emails had a substantial negative impact on their customers’ experience. You must remember that at the time, email inboxes were a paid-for service, but more importantly, they came with a tiny amount of storage. It’s almost unimaginable to a modern user, but email inbox capacity was measured in megabytes rather than gigabytes! Large amounts of spam filling the inbox had to be dealt with regularly by the user to prevent their inbox from reaching capacity and blocking emails from friends and family and legitimate marketing.

The ever-increasing amount of spam hitting their customers forced old-school inbox providers to do something about it. They started out doing very basic stuff like figuring out what words typically were used in Subject Lines from spammers and then blocking email Subject Lines that contained them. Other tactics used at the time included calculating the ratio of text to HTML in the message and blocking those that did not conform to standards deemed to be legitimate. Remember those days?

The Solution

The advent of Gmail in 2004 completely changed the game. To begin with, every Gmail account came with one GB of memory of space, which meant that the inbox owner did not have to clear their inboxes as much. Think about the difference between having an inbox with a capacity of a couple of 100 MB versus 1 GB! Spam instantly becomes less problematic for you in terms of using up your storage.

The other thing Gmail brought to the party was much better algorithms for dealing with spam. They brought AI to the table, and suddenly, getting to the inbox was no longer just a matter of getting the proportion of HTML to text in your email right and avoiding certain words. Gmail started looking much more deeply at things like language IN the actual message, using text recognition, blocking domains spam email is originating from, analyzing the pattern of sends etc.

With Gmail wiping the floor with the competition, other inbox providers were forced to play catch up and, as a result, in today’s environment authentication is a much more important inbox placement factor than the content of the email. 

Deliverability requires adherence to SPF, DKIM, and DMARC best practices. These are a set of email authentication methods that prove to ISPs and mail services you are truly authorized to send email from a particular domain and are a way of verifying your email   server is sending emails through your domain. 

The Practice

What does this mean for today’s email marketers?

I think email marketers need to   first ask the question “do I have a deliverability problem or not”, because the issue around “Spammy” words in Subject Lines and how that impacts deliverability is very different for someone who has a problem with deliverability versus someone who hasn’t got a problem with deliverability. 

Let’s start with people with deliverability issues. If you are tackling a current deliverability issue, then the words used in your subject line are highly unlikely to be the problem. I would suggest that you should be thinking immediately about all the other authentication factors rather than your Subject Line. When it comes to deliverability, Subject Lines are the cherry on the cake – not the cake itself, so I doubt any deliverability expert worth paying would start with by looking at your Subject Lines.

Does that mean   the only people who should be concerned about deliverability when it comes to Subject Lines are people with existing deliverability problems?

The answer is no.

What we do here at Alchemy Worx and recommend to you is be proactive. We use Subject Lines to AVOID deliverability problems in the first place. Very few people would disagree with you if you said that the key cause of deliverability problems outside of authentication is engagement or lack of engagement. The more people you have on your list that do not find your emails engaging enough to open, the more likely you are to have deliverability challenges not to mention the fact you are leaving money on the table.

This is where Alchemy Worx Audience Management methodology comes into play. Audience Management is designed to improve deliverability by increasing the number of active people on the list. We use Subject Lines to deliver more customers that engage with your program. 

We constantly run subject line tests against every segment – active, inactive, high-value, low-value and everything in-between to ensure EVERYONE gets a subject line that is optimized to encourage opens, clicks and purchases. We help our clients grow their list of active customers AND keep them engaged!

You Get What You Give

This approach also generates significant amounts of incremental revenue previously left on the table. To give you a sense of how much, here is a quick example. At the beginning of the COVID-19 crisis we were asked to help a client whose acquisition budgets had been slashed to weather the storm. We recommended Alchemy Worx Audience Management methodology to them and began by testing against ALL their segments including their unengaged file (the biggest). We then calculated the rate and scale of movement between segments. We identified approximately 395,000 “active” customers who had opened an email within 180 days and some 935,000 “inactive” who had not opened an email in 180+ days.

After 5 months we were able to increase their engaged audience by nearly 70%! Reactivating nearly 250,000 customers with little or no impact on inbox delivery rates at all. 

What we found (as you will) is the Subject Lines that make unengaged people re-engage for the first time are often quite different from the Subject Lines that you use on a regular basis. Do not assume that a Subject Line that engages an active customer will also work on your inactives. 

The big problem for email marketers is that in terms of lift, Subject Line testing for deliverability gives you a much smaller return on an email-by-email basis than you would get testing for something else. So often, subject line testing with the goal of deliverability behind it doesn’t get much traction in the organization. By thinking of it in terms of audience management and running separate tests for your active and inactive customers, you improve long term deliverability without wasting Subject Lines that probably won’t work on your active list. It also means that you are much more likely to generate more $ when you do mail your inactive subscribers.

Given how much testing audience management requires us to do, we use Subject Line Pro a virtual subject line testing platform that delivers real, accurate results in seconds. With Subject Line Pro, you can create a virtual simulation of your subscriber base to predict likely open, click AND DELIVERY rates for any given Subject Line. Our proprietary algorithm quickly predicts Subject Line performance within 1-2% of actual results before you send the test. It also has a built-in library of several million Subject Lines ranked by how likely they are to succeed from which you can draw inspiration. By way of example check out the image below for some SPAMMY Subject Lines predicted to perform better than average for deliverability.

You can try out SubjectLinePro free for 3 months - no obligation (worth $1500). Please use WEBBULA as your Coupon at check out when you sign up.


Meet the Author

Dela Quist, is CIO of Alchemy Worx, the largest email marketing agency. He is a highly experienced expert email marketer with a strong background in digital media and advertising.

Services include: email marketing strategy, email marketing best practice, email campaign planning, email design, email copywriting, HTML email production, email campaign deployment, email delivery and reputation, spam filter avoidance, reporting, and analysis.

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