Resources Hub » Blog » 9 Factors That Affect Your Email Deliverability

Article first published September 2015, updated September 2019

“How can I help ensure my emails are being delivered?” The simplest question in email marketing might also be the one with the most complicated answer. As an email marketer, you want to provide killer content to your subscribers.

You want to see people sharing that content on Facebook and Twitter and talking about your brand. You not only want to see people opening your emails, but you want to see people engage with them in a meaningful way.

The kicker here is that it’s not just about creating beautiful, optimized emails. It’s also about better positioning your campaigns to reach the inbox, avoid spam filters, and then to get opened and acted upon by your subscribers. That’s where email deliverability comes in.

What is email deliverability?

Email deliverability is how you measure the success of your emails reaching the inbox without bouncing or being marked as spam. If you have issues with high bounces, flagging spam filters, or low engagement, you may have email deliverability issues.

In this post, we’ll take a look at nine things you may be doing (sometimes without even knowing) that are killing your email deliverability.

We’ll also explore some quick, easy-to-implement fixes that you can use to help build your sending reputation and improve email deliverability.

9 ways to kill your email deliverability

1. Leave your subscribers in the dark.

Sometimes, old adages are true; prevention truly is better than the cure. In the email marketing world, this means first building a solid, permission-based list where your recipients have expressly opted in to receive your emails.

But maximizing the potential of your subscriber list and the engagement level of your recipients requires more than just building a list of opt-in recipients—you want to start off on the right foot and send.

If someone signs up to receive emails from your brand and they don’t receive an email for six months, they’ve probably forgotten who you are and why they signed up to receive your campaigns. In email deliverability terms, waiting too long to send your first email is killing your chance of creating a good first impression in the inbox.

Instead, send an email at signup that encourages engagement and clicks and gets your recipients used to connecting with your brand in their inbox from day one.

Welcome emails should make your new subscribers feel like they belong there.

Source: Really Good Emails

Send consistently and regularly, though not too often. This can vary wildly depending on your industry and brand, though one email per quarter is probably too few and one a day, too many. With some testing, you should be able to find a sending frequency that works for you and your subscribers.

2. Send without custom authentication.

A large part of email deliverability comes down to taking every step possible to avoid being perceived as a spammer in the eyes of spam filters and your recipients.

One of the most definitive ways in which you can affect this is by authenticating your emails. Authentication allows ISPs to acknowledge the legitimacy of your email sends. By putting verified SPF and DKIM settings in place, receiving mailboxes have some verifiable information to cross-reference with your email campaigns and can more easily determine if your email is the real deal or fraudulent. Gmail cites authentication as one of their top recommendations for helping get your emails delivered to their users’ inboxes.

At Campaign Monitor, we automatically handle authentication for you, though we highly recommend you put authentication in place using your own SPF records and DKIM key for the best possible impact on your email deliverability. Usually, your network administrator will be able to help set this up for you.

By putting custom authentication settings in place, your emails are far more likely to be delivered.

3. Settle for single opt-in.

Confirmed (or double) opt-in means that, after people select to sign up for your email list, they receive a confirmation email they must use to confirm their subscription.

Confirmations are great options for a double opt-in.

Source: Really Good Emails

Not only does a confirmed opt-in help protect you from erroneous signups and spambots, but confirmed opt-in lists see better results with almost every engagement metric, other than the sheer number of sign-ups in comparison to single opt-in lists.

Confirmed opt-in lists are more engaged from the start and, by using confirmed opt-in, you can more effectively build your sending reputation by sending to a more engaged and active list.

4. Send from a free domain email address.

Every part of your campaign needs to authoritatively communicate to your recipients and spam filters that you are who you say you are.

Using a from address that’s a domain other than your own is a big no-no. Similarly, using a free domain email address such as Hotmail, Yahoo, or Gmail is also a bad idea. Yahoo, Gmail, and other ISPs will automatically mark your emails as spam if you send commercial or bulk email to an email address at their domain, from the same domain, under revised DMARC policies.

Instead, use an official company address that clearly communicates who you are. Virgin uses [email protected] for their Experience Day campaigns—this lets people not only know whom they’re receiving the email from (Virgin), but what they’re receiving (a newsletter), and which part of the business they’re receiving the email from (Experience Days).

As a global brand with products and services spread across many industries, using a send-from address tailored to this particular part of the business is integral for strong email deliverability.

Be sure to use an address at a domain or authenticated sub-domain that you own and that your recipients expect to hear from. Not only will this help prevent ISP filters from blocking your emails, but this will also be instantly recognizable to your recipients and help build the sending reputation for your domain.

Get our guide to avoiding spam filters to ensure your emails get delivered.

5. Write unclear or spam-flagging subject lines.

Your subject line is the welcome mat of your email and, often, issues with subject lines are as simple as this: If your subject line makes your email look like spam, then people and the spam filters ISPs put in place to protect them will probably think that it’s spam.

Avoid ALL CAPITALS, excessive and unnecessary use of punctuation (!!!), and use symbols and SP$C!AL CH@RCT3RZ sparingly, and only when relevant.

Also, ensure that your subject lines match the content of your email—no one wants to be promised a trip to a theme park and end up at the dentist.

An “RE” or “FWD” prefix when there’s been no such previous contact or email exchange is misleading. Similarly, does your email require “urgent action” and is your offer “exclusive” and “one time only” designations? If not, leave them out.

Best practices for the rest of your email copy also ring true for your subject lines. Be concise, as many email clients may truncate subject lines with too many characters. Use personalization, be creative with your copy, and be clear with your subscribers about what the email contains.

6. Design emails with too many images.

A historic spam technique was to send emails that contain just one image or many images and very little text in HTML emails in order to bypass spam filters that were based primarily on spam keywords.

Spam filtering is now based much more on sending reputation than content, though image to text ratio does still carry some weight with spam filters and is something you’ll want to spend time getting right.

Emails with very little copy and many images, or simply composed of one large image, can be hallmarks of spammers. By composing similar emails, you can run the risk of your email being flagged as spam.

Remember, many email clients or devices aren’t configured to display images by default. If your email is composed almost entirely of images that aren’t displayed by a recipient’s email client, this renders the content of your email unreadable and certainly not something your client can interact with easily.

Too many images can look spammy.

Source: Really Good Emails

Instead, design your emails with this in mind and ensure you balance your images and copy so that your email makes sense and is engaging in the event of the images not being displayed. Always use alt text for your images, so, even if they don’t render, your subscribers will have some context for what the images are.

7. Use URL shorteners.

The use of URL shorteners is a notorious technique used by spammers to hide the nature of URLs they link to and, as such, rank high on reasons spam filters can block your emails, even if the links themselves are legitimate.

Avoid using URL shorteners and, also, avoid inserting the full URL link as text in the body of your email. Instead, create a hyperlink with the appropriate text and ensure all your links go to legitimate domains and are valid and functional. By replacing URL shorteners with clear and attractive CTAs, you’ll also drive traffic and see more click-throughs on your sends. This is another piece of the sending reputation pie that can further boost your email deliverability.

8. Make it difficult to unsubscribe.

While an unsubscribe link must be included in every email sent through Campaign Monitor, we also recommend that it be simple and easy for your recipients to find.

Hiding your unsubscribe link in a wall of text with an 8pt font will only serve to frustrate your recipients, should they be attempting to unsubscribe. In our experience, the more difficult you make it to unsubscribe, the more likely your recipients are to mark your email as spam.

Roku does an excellent job of making their unsubscribe link easy to find. Instead of including it in a large wall of text, they set it apart from the other information so users can find it and click it, should they wish to remove themselves from the list.Your unsubscribe link doesn’t have to be a primary focal point, but it does have to be easy to find.

Source: Gmail

Make your unsubscribe option clear and easily visible and, better yet, add a permission reminder message alongside it to remind people where they signed up or gave you permission and point them towards unsubscribing if they’re no longer interested in receiving your emails. Your recipients will appreciate this honesty and clarity, and an unengaged recipient choosing to unsubscribe is always preferable to receiving a spam complaint.

9. Send to unengaged recipients.

In email deliverability terms, low open rates are a clear signal to ISPs that your recipients are not engaged with you, your brand, or your content. That lack of engagement is a factor in the delivery of future emails and can even lead to your campaigns being blocked. Think of it as a snowball threatening to become an avalanche—your low open rates mean that ISPs block your future emails, which leads to even lower open rates, which, in turn, leads to a further lack of engagement.

Considering taking action with a list that you’ve nurtured and grown over a long period of time may be difficult, but what’s worse is this: You could be damaging your sending reputation by continuing to send to people who’ve never opened your emails, and you’re paying for the privilege.

Instead, check in with your least engaged subscribers by sending a re-engagement campaign asking them to confirm they wish to remain on your list. If you send an email every day or every week you can send a re-engagement campaign every 3-6 months.

If you send an email once a month or less frequently, you can send an annual re-engagement campaign. Anyone who hasn’t opened an email or clicked a link in 12 months or more should be removed from your list, as permission to send emails has expired and you run the risk of low open rates, high bounce rates and spam complaints, all of which damage your sender reputation.

Such a campaign is a great way to reach out to your inactive recipients and get them regularly reading your emails. Let people know that you understand that they haven’t been active recently and remind them why they should be reading your emails. Highlight your great content, be open and clear about your sending frequency, and invite them to continue receiving your emails, only if they want them.

After you’ve done a re-engagement campaign, you’ll be able to easily identify any recipients who are genuinely unengaged so that you can remove them from your list. By amending your list so that it’s full of active recipients, you’ll see greater levels of engagement and, in turn, receiving ISPs will notice a higher volume of emails being opened and clicked compared to emails sent. Build and maintain your sending reputation to positively affect your email deliverability in the future.

Bonus: Improve your email list with these metrics.

Unfortunately, many email marketers don’t know that their campaigns aren’t working until it’s much too late. This is something that could easily be avoided by simply monitoring a few key email metrics once you’ve sent off your campaign to your subscribers.

Monitoring your email metrics is vital to your email campaign success.

Source: Campaign Monitor

Most quality email service provides its clients with email insights and reporting. These tools allow you to carefully monitor key email metrics to help you determine what’s working and what isn’t. When it comes to the success of your email campaigns, you’ll want to keep an eye on the following metrics:

  • Open rates
  • Click-through rates
  • Delivery rate
  • Unsubscribe rate
  • Spam rate
  • Bounce rate

While there may be plenty of other metrics available to you, these are some of your most vital. Why? Because they tell you how active your list is and how well they’re engaging with your content.

Trends you’ll want to watch for include:

  • A decrease in open, click-through, and delivery rates
  • Increases in unsubscribe, spam, and bounce rates

These trends will show you who’s interacting and who isn’t. This is a vital piece of information when it comes to maintaining your email list hygiene. Once you start seeing those negative increases, you know it’s time to start removing unhappy customers or those who simply aren’t receiving your messages or interacting with them.

One of the best ways to do this is by sending out a regularly scheduled email campaign asking your users to update their preferences or “click” to remain on the mailing list.

 Email list hygiene is vital to your marketing success, so keep it full of people who want to be on the list.

Source: Really Good Emails

With a campaign like this one from Framebridge, those who click on the CTA will remain active on your list. However, those who ignore the CTA or email entirely should be flagged and removed immediately, as they clearly have little to no interest in following through with your brand.

Wrap up

Email deliverability is an ever-changing aspect of email marketing and should be on the mind of every marketer. By implementing some of the following recommendations, and better positioning your campaigns for success, you should see improvements in the delivery of your emails and an improved ROI for your email marketing.

Recommendations to keep in mind:

  • Stay relevant in your subscriber’s inbox by being consistent with your messages.
  • Custom authentication is your friend.
  • While single opt-ins are okay, double opt-ins make sure your list is comprised of the right subscribers.
  • Where you’re sending from matters—free domains aren’t so reliable.
  • Avoid spam-flagging subject lines.
  • Images are great, just don’t overload your reader.
  • URL shorteners should be avoided.
  • Make the options to unsubscribe as simple as possible.
  • Maintain email list hygiene.
  • Monitor your email campaigns success.

Are you in need of a refresher on email marketing metrics? Then check out our short guide on 17 metrics every marketer needs to know.


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