Nicole St. Germain
19 min read
No matter how amazing your email content might be, if it never reaches your subscriber’s inbox, all your work will forever go unnoticed. No one will find out about your products, you won’t gain that strong trust with your potential customers, and it will be extremely difficult to make a living with your online business. But finding your way into an inbox isn’t as simple as just sending an email. You have to take email deliverability into consideration.
When it comes to email marketing, email deliverability can be one of the most confusing concepts. So to help you know how to get your content from your email service provider (ESP) to your subscriber’s inbox, today I’m breaking down the basics of what email deliverability means, how it affects your sending, and how to increase your chances of good deliverability.
First off, there will be some words and concepts that might sound like gibberish to anyone new to this topic. If you fall in this category or just want a little refresher about what I’m talking about, here’s a handy cheat sheet of deliverability terms you can download now to reference as you read.
Deliverability Terms Cheat Sheet
Deliverability is a partnership between your IP/domain reputation, your email content, and your subscribers' email provider. As an ESP, our goal at ConvertKit is to get you in the door, meaning inbox deliveries within email providers like Gmail, Outlook, and Yahoo. There are quite a few factors that determine how your email is filtered once it’s received by an Internet Service Provider (ISP), but your IP/domain reputation are likely the most determining factor on whether your messages are delivered into an inbox or a spam folder.
While your IP/domain reputations are determined through a combination of factors, research within our industry has shown that the most important factors are: Subscriber Engagement, Limiting Negative Metrics, Authentication, and Content. So let’s talk about how these four things come into play in terms of your email deliverability.
These days ISPs are paying close attention to how previous customers of that provider have interacted with email sent from your domain/IP. That means the future of your deliverability can depend on what your subscribers do with your emails right now.
For example, Gmail often will make assumptions on where to filter your email based on trends seen from their customers. That means if the majority of subscribers are deleting your emails without opening them, marking the messages as spam, or taking no action on it all, Gmail will make the determination to increase spam or promo folder filtering for your IP/domain and will lower your overall reputation with Gmail.
On the other hand, if a lot of people are opening and clicking (showing positive engagement), Gmail is more likely to deliver future messages from your domain and IP into their inbox. This makes it extremely important to make sure that subscribers are receiving email content they actually want and on an expected schedule established upon signing up for your email list.
High levels of user spam complaints and hard bounces can be the quickest way to go from good IP/domain reputation to bad. Spam complaints at high levels (> 0.3%) give email providers indicators that a marketer is potentially sending unsolicited content, which is a violation of CAN-Spam or CASL regulations . Marketers observed exhibiting this type of behavior will lose trust in the eyes of ISPs, which will typically result in very poor inbox placement levels.
When ISPs observe spikes in hard bounce levels this often raises questions about the marketer's list collection and hygiene (or cleaning) processes. Purchasing or using third party lists can often result in high levels of hard bounces based on the fact that many of these types of subscribers are un-verified. Many companies that provide these types of lists use web-scraping tools to gather email addresses from all over the Internet (many of which are spam traps), and they sell them to marketers that are looking to grow their client base. This is a huge ‘No-No' in the eyes of an ISP and will often result in drops in your reputation.
Sending to older segments of subscribers can also show spikes in hard bounce levels. A general rule of thumb is that if a subscriber or list hasn't been sent to in over a year, it's best to get rid of that group. While this can be a scary thought, as many marketers never want to throw away subscribers, we have to remember that ISPs value quality over quantity.
We have to always look at the big picture here. Sending to an older list may provide you with a small amount of conversions, but if it results in all of your Gmail subscribers receiving their email in their spam folder going forward, is it really worth it?
ConvertKit offers assistance in setting up your SPF and DKIM records to align with sending through our platform. Whether you're sending your email through convertkit.com or through a custom domain setup (ck.yourdomain.com), we look to make sure that emails sent through your account show ‘Passes' for SPF and DKIM authentication levels.
Before an ISP delivers an email they first examine the email headers of that message, looking for permission for your domain to be sent across our IP addresses. If the SPF and DKIM records show failures within the message headers, your domain does not give permission for it to be sent across any of the IPs that are not stated within these records.
Here’s how it works:
By default when you get started with ConvertKit, you're sending on one of our sending domains. It usually looks something like ckmail2, 3, 4, etc. We have about five of these spread out among customers so multiple ConvertKit customers can be using the same sending domain. There are both benefits and disadvantages to how this affects you and your email deliverability.
If you're just starting to build your domain's reputation, using a sending domain other customers are using and have been using is a great thing. It quickly helps build up your reputation. However, it is possible that the consequences of another customer's poor sending practices can impact you negatively.
We have a lot of controls in place to prevent that from happening and we regularly redistribute our customers across our sending domains, but it’s still possible that a shared sending domain will negatively affect your deliverability.
For our customers who are most serious about deliverability, we offer a custom sending domain that allows you to rely solely on your own domain reputation. To find out more about custom sending domains and how to set one up, contact our Customer Success team.
Your content plays a big role in how an email is delivered as well. Think of a typical newsletter you receive from a retailer, like Target or Bed, Bath and Beyond. They usually contain a ton of pictures with really complex HTML that almost mimics visiting their webpage in your browser. When Gmail sees messages like this, with primarily images and complex HTML, they will often filter it as a promotional email. At Convertkit, we put a major emphasis on simple emails like the ones you write to a friend, which helps us avoid those promo filters.
Simple, plain text emails are more likely to be delivered into a primary inbox, period. Even though we recommend sending plain text emails to improve your deliverability, there still aren't any absolute changes that can be made to guarantee inbox placement within the Primary Tab.
Recent studies have shown that the usage of Gmail Tabs has dropped to roughly 33% (a 66% decrease in users since 2013). The prevailing thought here is that this filtering will have less of an impact going forward because those Gmail users that are savvy enough to set this up are usually the same users that will routinely check these folders.
Now that you know what affects email deliverability, let’s increase your chances of hitting those primary inboxes, shall we? The four high level deliverability concepts we’ve covered can be broken down into actionable, daily takeaways. Here’s how…
Email deliverability doesn’t have to be rocket science. There are very easy practices you can put into action every day and with every email you send to help increase your deliverability chances. Here are 10 (easily actionable) email deliverability best practices.
Like I said earlier, purchasing and using third party lists will result in high levels of hard bounce based on the fact that many of these types of subscribers are un-verified. So while you have a big list of, let’s say 50,000 subscribers right up front, the trouble is that they didn’t choose to be on your list. A vast majority of those emails will go straight to the SPAM folder, many more will mark them as SPAM once they’re opened, and then another large number will unsubscribe immediately. So even if you’re left with a few thousand in the end, they aren’t people who are choosing to hear from you.
Some opt-in offers are better than others when it comes to building an email list full of qualified subscribers. For example, because giveaways and freebies attract a wide range of people, you’ll most likely get a high volume of signups that will never open your later emails or might even move them to their spam folder. Their negative engagement can eventually end up sending your emails to other subscriber’s spam folders as well.
To combat this, make sure your opt-ins are always targeted to an audience that would be interested in your topic. You always want to be attracting readers who would likely open your emails and eventually become customers.
So if you’re planning on running a contest with giveaways, make sure you’re setting yourself up for the outcome. If you’re wanting to grow your list with a targeted audeince, create a giveaway that only that group will want. Or if you just want to get your name out there and build a large list, create a giveaway that will appeal to a wide audience.
Like I said earlier in the content section, simple emails will always deliver better. Even when it comes to images or tables in your emails, too many will decrease your deliverability. You can read more about our theory on why text-based emails are the way to increase your email deliverability in our post Why Fancy Email Templates Aren’t the Answer.
Images in and of themselves are not bad. Everyone loves a beautiful picture or graphic and they often help convey a thought or point quicker than actual text. But when you use an image, make sure to write accurate alt text or title instead of simply using the image’s file name. This way if an image gets blocked for any reason, a reader will still know what your image is. This also helps prove that a human sent the email instead of a spam robot.
How to- After you’ve added an image to your email in ConvertKit, click the image again and then click the edit button that pops up. In the edit box, write a title for that image that describes what is happening in your image, ie- your call to action, the details of a promotion.
Sadly, because of those spammers out there, there are some words that have developed a bad wrap. When used in subject lines for emails, these trigger words can signal the possibility of spam and usually will send an email straight to the abyss. Here are a couple of those words to avoid in your email subject lines (and your content, if you can):
Setting up the double opt-in process adds an extra layer of subscriber qualification for you. If a subscriber clicks through a double opt-in:
With ConvertKit, setting up a double opt-in process is as easy as clicking a button.
Again, setting up a custom domain for your reply-to email address will increase your deliverability. That means your days of using freemail like Gmail, Hotmail, and Yahoo are over. Learn how to setup your custom sending domain with ConvertKit: contact our amazing Customer Success team.
No matter how exciting or targeted your content is, there will always be a group of subscribers who aren’t engaged with your emails. Since those unopens can affect your email deliverability, it’s a good idea to run a re-engagement email sequence every 90 days to filter out what we call cold subscribers. Cleaning out your subscriber list will help it be healthy and high quality (plus, you’ll save money).
Sometimes email to new subscribers end up in their spam folder for reasons beyond your control. If those subscribers end up getting in contact with you asking where the email went, ask them to check their spam folder and take a second to move that email from the spam folder to their inbox. It might sound like a silly request, but doing this teaches that ESP that your email actually belongs in the inbox. Doing this will not only help with that particular subscriber's emails, but it will also help similar users whose emails might be ending up in spam as well.
The last thing I want to mention that often gets mistaken for a deliverability issue is the subject line. While a subject line could potentially impact deliverability, it has it's greatest impact on engagement. A subject line is the first and sometimes only thing a subscriber reads of your email. If it doesn't clearly communicate what the email is going to be about and entice them to open it, then they won’t. Subject lines are often the simplest thing to tweak that have the greatest impact on opens and clicks.
Ready to start increasing your chances of optimized email deliverability? To find out where you stand right now, there are a couple tools you can check out. MailTester and GlockApps both test against Spam Assassin to tell you how your emails are delivering.
Once you’ve got that information you can start putting all those email deliverability best practices I talked about into place. Then it’s time to watch those clicks and conversion rate numbers rise.
Blacklist-This is a list of IP addresses of known spammers, or “spam friendly” servers. If your IP address is on the list, it won't let your email through.
CAN-Spam – Short for ‘Controlling the Assault of Non-Solicited Pornography And Marketing Act of 2003,' this law outlines rules for commercial email, establishes requirements for commercial messages, provides email recipients with the right to make you stop emailing them, and lays out consequences for violations of the Act.
CASL regulations- This is Canada’s anti-spam legislation. It’s similar to CAN-SPAM in that it protects consumers against receiving unwanted email but different in that it is much more specific about permission and what is considered “opt-in”.
Domain– Similar to an IP Address, domain names refer to locations of servers and devices connected to the Internet. Domain names can represent many different IP addresses.
Domain Name System (DNS)- DNS is an Internet service that translates domain names into IP addresses.
Domainkeys Identified Mail (DKIM)- DKIM was designed to prevent domain spoofing, or someone pretending to send from your email domain, when they really aren't. DKIM uses cryptographic authentication, which means the records we generate will be unique to you and your domain. Read more about DKIM here.
Double opt-in– With a double opt-in a user is sent an email with a confirmation link after they initially opt-in to your list. After the user clicks the link, they are added to the ongoing email communication. This is a recommended way to build a healthy email marketing list.
Email service provider (ESP)- ESPs provide platforms to send commercial and transactional email on your behalf. ConvertKit is an ESP.
Hard bounce– A hard bounce means that the email address is invalid and should not be sent to again. The email might belong to an unknown user, the content of your email might have triggered their spam filter, or the server might have seen too many other contacts marking your email as spam. When a contact’s email returns a hard bounce, they will be marked as ineligible the next time you include them in a send.
Internet Service Providers (ISP)- ISPs provide mailboxes to end users as part of their paid services. These are generally your cable or Internet providers, such as Comcast and Verizon.
IP Address- A number that uniquely identifies any device connected to the Internet. “IP” stands for “Internet Protocol.” Similar to how a street address helps people find buildings, an IP Address helps computers find each other on the Internet.
Open rate- The percentage of recipients who opened your email message. When someone clicks on an email, an image pixel in the email loads and is counted as an open.
Sender Policy Framework (SPF)- SPF was specifically created to protect against sender address forgery – spammers pretending to send emails as you. An SPF record in your DNS Settings gives email providers something to check, to make sure the emails are really coming from you. Read more about SPF here.
Sender score/reputation- This is basically your rating as an email sender. Return Path’s sender score tool is a free reputation rating tool that rates your outgoing mail server IP on a scale of 0-100. It’s used by mail servers, allowing them to quickly sort email IPs and decide what to do with your email. A sender score that is + 90 is considered a good sender score.
Single opt-in– If an email marketer uses a single opt-in, this usually involves taking a user's form entry and immediately adding that person to a live email list.
Soft Bounce – A soft bounce means that the email temporarily failed to reach its intended recipient. The email will be resent for up to 72 hours or until it’s either successfully delivered or it fails more permanently. Recipients that return soft bounces will still be eligible for future email sends.
Spam complaints (Marked as Spam)- This is the number of contacts that actively marked your email as spam. Contacts that mark your email as spam are automatically unsubscribed from all of your email. Please be aware that Marked as Spam is not the same as an email going into a spam or bulk email folder.
Spam trap/Honeypot– A planted email address designed to catch spammers. For a time, email that hits a dead email address will return a hard bounce. When the mail server sees continued traffic going to the dead address, it can turn the email into a spam trap, accept the email, and report the sender as a spammer.
Whitelist– The opposite of a blacklist, this means your server is considered spam-free or is an “approved sender.” It’s often used by email applications to allow users to mark whether or not they trust emails from specific senders, this overrides some of the filtering that may exist from the ISP. You can also apply for whitelisting programs that a few ISPs offer. While not a guarantee to end up in the inbox, a sender may receive preferred delivery as long as they stay within the proper thresholds of the program.
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