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Increasing Email Deliverability

Last month, I introduced a new series of blog posts – all about common struggles that marketers face when implementing a new marketing automation system.  Last month, we talked about avoiding hurdles by planning ahead.  This month, I want to look at a more specific issue that has come up a lot recently – email deliverability.

When you send out an email to your list of contacts, you want…no, you expect your email to show up in everyone’s inbox.  And that is not an irrational expectation.  After all, why would we be advocating marketing automation if the emails that you spend so much time creating are not ending up in your prospects inbox?

According to Return Path’s Email Intelligence Report Q3 2012, 18% of permission-based email in North America never reaches the inbox: 5% is classified as spam, and the remaining 13% simply goes missing.

So the question that inevitably follows is “What can we do to insure that all of our email is delivered?”  

There is a little work required on your end to increase your deliverability rate.  Below is a list of some best practices – from email content suggestions, to technical adjustments – that will increase the likelihood that all of your messages will be delivered as expected.  It’s a long read, but each of these items can contribute in determining if your email is ultimately going to make it in front of your prospects.


Sender Reputation

The good news is that your reputation as a sender is the most important variable when it comes to getting your emails delivered.  So, as long as you don’t have a reputation for sending spam, you should be in good shape.  Note that if you are purchasing lists, you should be buying well-targeted lists and only sending relevant info to these contacts, or else you run a risk of increasing spam complaints and hurting your reputation as a sender.

Additionally, the email marketing/marketing automation tool you are using also contributes to the reputation.  Since your emails are being sent from their server, it is important that you are using an email marketing or marketing automation tool that has a good reputation.  For example – when using SpamAssassin to calculate the spam score of an email, the marketing automation software we use (Act-On) actually lowered the score by 0.7 points, showing that sending from their server has a positive impact on our reputation.

You can monitor your sender reputation using products such as Cisco Sender Base or Return Path Sender Score.  These are both paid third party tools that help you monitor any shifts or changes in your reputation.



One active step that you can take to help increase your sender reputation is to authenticate.  Authentication lets the Internet Service Provider (ISP) know that the sender is who they say they are. There are three methods of authentication, listed below.  With the help of your IT team and your marketing automation service provider, you are able to implement one or all of these, helping to validate yourself as a trusted sender.

1. DKIM (DomainKeys Identified Mail)
DKIM is a technology designed to make it difficult for spammers to steal the identities of legitimate organizations. This authentication technology allows senders to “sign” a message to prove that it really did come from them. More Info >

2. SenderID
Similar to DKIM, SenderID addresses spoofing and phishing by verifying the domain name from which e-mail messages are sent.  Sender ID validates the origin of e-mail messages by verifying the IP address of the sender against the alleged owner of the sending domain. More Info >

3. SPF (Sender Policy Framework)
This is another technical method to prevent sender address forgery. Unlike DKIM and SenderID, which protects the header sender address, SPF protects the envelope sender address, which is used for the delivery of messages. More Info >


Past Engagement Aids Future Deliverability

Many email service providers have said that if a user is not opening or clicking on messages from a sender, then, over time the messages from that sender will start being automatically sent to the spam folder.  Likewise, if messages from a specific sender are always opened and clicked, then future messages from that sender will continue to show up in the inbox.

What that means for marketers is that you need to be creating email messages that are targeted and relevant to your subscribers.  Make sure they have a reason to open and click, because if they are, then your emails will continue showing up in the inbox.



The more steps that are involved for a person to opt-in to your list, the more likely your messages are to be delivered.  This ranges from a purchased list, which usually sees lower deliverability rates, to a double-opt in that requires the individual to opt-in, then click through an email to confirm the subscription.  This type of opt-in generally sees the highest rate of deliverability, but can often result in fewer total opt-ins due to the added step.

Whenever you have individuals opting into your list, you should give clear instructions on adding your email address to their address book, both on the sign-up page and in your first welcome/confirmation email.  If your email address is in their address book, you increase the likelihood of making it to the inbox and not getting blocked by spam filters.

And don’t forget to be clear about what the user is opting into.  A leading cause of spam complaints is a disconnect between what the recipient thought they were opting into and what they actually received.  Be honest and open about what they should expect to receive from you.


Subject Lines

One of the best things you can do to encourage engagement with your message is to optimize your subject lines, as this is what recipients will use to determine if they are going to open your message.  And as stated earlier, engagement with your message will help insure future deliverability success.

You should use the subject line to clearly and accurately describe the content of the email, highlight the benefit of opening the email, and/or create a sense of urgency.  Most email programs display the first 30-50 characters of the subject line (only 20-30 on mobile), so try to keep your subject line length within this range.  Also, use common sense and avoid subject lines that look like spam:

  • Excessive punctuation !!#@$??
  • Symbols such as $$$$ or *****
  • Using RE:


Email Content

While your reputation and recipient engagement with your messages have become the most important aspects when determining the deliverability of your emails, the content itself is still important.  There are a few rules you should follow to make sure you aren’t trapped by spam filters based on the content of the email message you are sending:

  1. Don’t use Flash or JavaScript. Flash doesn’t work consistently across email clients, and JavaScript is usually disabled.
  2. Don’t embed your text and graphics into a single image and don’t use large images.  These things are commonly used by spammers and will cause your message to end up in junk mail folders. Instead, use a good ratio of text and images throughout the message (no more than one image per article or offer), use small images and link them to larger images on your website.
  3. Avoid busy background images that make your text hard to read.
  4. Using the recipient’s name within the content of the email itself has been shown to increase conversion rates.
  5. Use alt text for your images.  This allows recipient’s whose email service provider blocks images (Gmail) to know what images are in the message, increasing the likelihood that they will choose to display them.

Here are some other email best practices that I outlined a while back.


Check Your Spam Score

Similar to the sender reputation scores mentioned earlier, you can use tools such as SpamAssassin to check the spam score of individual messages.  These tools test the message for common spamming techniques and give you a score that corresponds to the likelihood of your message being marked as spam.  A spam scoring tool is built into most of the good marketing automation platforms.

Your score should be as close to 0 as possible.  Any signs of spam will result in some of your contacts not receiving the message, so make any changes necessary to bring this score down as low as possible.


List Cleanliness

The last thing you should do to insure good deliverability of your messages is to keep your lists clean.  Your marketing automation tool should suppress bounces and opt-outs automatically, but you will need to set a scheduled time to remove inactive records (contacts who have not opened or clicked on any messages) on a regular basis – quarterly or yearly is usually fine.

Also, regularly email your lists. Lists that aren’t emailed frequently are more likely to increase bounce rates and have outdated addresses.

While there is no magic process that will guarantee 100% delivered each time, if you follow all of the tips outlined here, then you should be well on your way to high deliverability rates.


Other Helpful Resources

Act-On Email Deliverability eBook –

Marketo Email Deliverability eBook –

Act-On Email Deliverability Datasheet –

Marketo Email Deliverability Cheat Sheet –

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