Picture This: You are about to flip the switch on what you hope to be a blockbuster campaign. You and your team have been working nights and weekends to prepare. Your landing page is ready. Your campaign emails are written, designed, and ready to go live. But what about your email deliverability rate? How does it rank? Heck, do you even know what email deliverability is?

In this article by our Director of IT, Kendall Longley, you'll learn all about email deliverability and the steps you can take to ensure inbox success.


Every single day, there is collateral damage in the ISPs' endless war on spam. Good campaigners pitching legitimate services and worthy causes are struggling with email deliverability. ISPs are constantly tweaking their methods of catching spam and spammers - from zeroing in on suspicious subject lines to blocklisting suspicious IP addresses. No system is perfect, and legitimate email campaigners are often caught in the crossfire.

Just a few years ago, ISPs measured just two things: hard bounces and spam complaints. If your hard bounces were under 5% and spam complaints within 0.10% (a tenth of a percent) threshold — that's one complaint per thousand emails — you were considered reputable. Today's ISPs assemble several metrics, including user click-through rates, to define your overall score. To make matters even more complex, the formula they use is constantly changing. Things are getting more complicated in the ISP email wars. The good news is you don't have to be an innocent casualty - if you take the right steps now.

Email deliverability is an important - and most overlooked - element of every email campaign. The sooner you address the factors that impact deliverability, the better to protect yourself in the ISP email wars. Preferably, right now! Email campaigns get results. But to succeed with it, you must address deliverability.

Deliverability Rates and Open Rates: Two Important and Different Metrics

As a campaigner, you've probably heard of the term open rate. Open rate reflects the percentage of people who end up opening your campaign email in their inbox, rather than marking it as spam, ignoring it, or deleting it without reading it.

The open rate pertains only to the emails that make it to the recipient's inbox. The deliverability rate considers all the emails that, for whatever reason, don't get to the inbox in the first place. Let's face it: nobody is going to open an email that they haven't even received. Yes, good subject lines and strategic sending times matter, but without a consistently high rate of deliverability, subject lines and sending patterns won't make much of a difference.

Campaigners typically measure the success of their email campaign by the open rate. However, the open rate doesn't tell the whole story. Let's say the open rate for your email campaign is 20%. 1 out of every 5 recipients - who received your email - took the time to open it. Sounds good, right? But what if you have a lower-than-average deliverability rate of 50%? That's going to be a big problem!

It's critically important to distinguish between intended recipients and actual recipients. Among actual recipients, your open rate stands at 20%. But among intended recipients, your open rate is reduced by half, to just 10%. That's half as many opens, half as many donations, and potentially half as much revenue generation from your email campaign. Yikes! NOW you can see why deliverability matters so much!

How ISPs Identify Spammers

Since spam is so incredibly annoying to just about everybody, it's no surprise that ISPs are waging open war against spammers. The first step in any war is identifying the enemy. ISPs use the following tools, signs, and signals to distinguish the bad guys from the good guys:

Spam traps — Spam traps are old inboxes ISPs reactivate to identify illegitimate emails. These addresses have never opted-in for your email, so whatever hits their inboxes is identified as spam.

Hard bounce rates — A hard bounce means that the email address no longer exists or that the ISP does not recognize it. Both are indicators for spam. A soft bounce can come from a temporary problem with the recipient's mail server. But soft bounces can turn into hard ones if the mail can't be delivered after several tries.

Complaint rates — Chances are you've hit the "mark as spam" button on annoying and/or sleazy marketing emails that pushed you over the edge. Each time a recipient marks your campaign email as spam your Complaint rate increases.

Email volume — If you are sending thousands of emails or more, realize that you are under the ISPs' microscope. They will be watching you extra closely for suspicious activities. If you are a high-volume sender, you can't afford not to be on your best behavior.

3 Best Practices for Good Email List Hygiene

A good sender reputation depends on good data hygiene. Your sender reputation depends heavily on the quality of your mailing list, and the quality of your list depends on the care you take in keeping it clean, accurate and up to date! Here are three tips for you: 

1. Use only opt-in lists, and don't use lists where end users have opted-in to someone other than yourself. Purchasing an opt-in list from a third party — who may be in a different industry — is very risky. Make it as easy as possible for recipients to unsubscribe. Offer multiple opt-out paths, generate regular re-permission campaigns and clean lists of inactive subscribers frequently. These are the best ways to avoid spam complaints and hard bounces, which can seriously damage your reputation.

2. Be vigilant about from addresses, subject lines, and email content. ISPs like to see a from line that identifies you, rather than a third party, as the sender. Check frequently which trigger words set off spam filters (these are constantly changing) and use best-practice content creation.

3. Be cautious about email frequency. Sending too many emails in too short a time could end up making frustrated recipients who classify your email as spam, even if they opted-in with you.

Incorporating these steps as part of the preparation for your campaign will help you earn a high deliverability rate which is key to achieving and keeping the trust of ISPs.