The complete guide to email deliverability

The 10 factors that hurt email deliverability

Email deliverability is complex by nature, and there are many factors that influence it. Below are 10 to take into consideration.

1. Poor reputation

Poor sender reputation has a large impact on email deliverability, specifically, domain reputation and IP reputation. Let's take a closer look at each reputation type.

Domain Reputation

Domain reputation is how ‘trustworthy’ a domain is and is affected by the quality of the sender’s emails, including the quality of their recipient list.

Mail providers like Google determine whether recipients enjoy the content they are emailed by that domain, and give the sender a rating based on things like open rate and replies, which impacts email deliverability.

Having a bad domain reputation, whether due to non-engagement or user complaints, can cause emails from a domain to be filtered to the spam folder by default or be, in effect, ‘blacklisted’ with a provider so they aren't delivered.

IP Reputation

IP (internet protocol) reputation is a measure that assesses the quality of an IP address to determine its legitimacy.

A positive IP reputation helps email receiving networks decide whether to deliver your email or block it from delivery. It can also be used as a determining factor of whether traffic from the IP is delivered to the inbox or spam folder (though domain reputation tends to be a larger contributing factor in such decisions than IP reputation).

Actions that harm sender reputation include – but are not limited to – the following:

• How many emails are marked as spam?

• How many emails are left unopened?

• How many recipients unsubscribe or opt-out of email communications?

• How many emails bounce?

The above actions relate to recipient engagement, which we will explore more below. Since sender reputation is built upon the positive or negative responses of recipients, poor engagement is the cornerstone of poor reputation.

2. Poor engagement

Poor engagement refers to negative activities on the recipient’s side that can lead to poor sender reputation.

Poor engagement may involve any and/or all of the following:

• High bounces (≥5%)

• Low opens (≤15%)

• High complaints (≥.05%)

• High unsubscribes (≥1%)

Note: The above metrics are a general threshold for ongoing poor-engagement trends across multiple bulk sends.

Engagement terms to note

Opens

Open rate is an email marketing metric that measures the percentage of emails that are opened by recipients (as opposed to emails that are left unread, deleted, marked as spam, or undelivered).

Clicks

Click-through rate is the proportion of visitors who follow a hyperlink to a particular website or landing page.

Bounces

A bounce is when an email is returned to the sender because it cannot be delivered. This can occur for multiple reasons and can be categorized as a ‘soft’ bounce or a ‘hard’ bounce.

Hard bounce

A hard bounce equates to a 'hard stop' received by the sender from the recipient-side server. It can be due to a misspelled or disabled address or to an outright block of the sender. Essentially, it means that either the address does not exist or the address wishes you to think that it doesn’t exist and discontinues any further sending.

Soft bounce

A soft bounce equates to a temporary issue of some sort. It can be due to a temporary block, a connection issue, or a myriad of technical issues surrounding the email receiving process. Essentially, it means there is a problem at this time that may be resolved at a later date.

Delivered

Delivered or 'delivery rate' is the amount of subscribers whose email delivery attempts were accepted by the receiving server, as opposed to bounces or invalid attempts to suppress addresses.

Unsubscribe

Unsubscribe rate is the amount of email subscribers (newsletter, product updates, etc.) who choose to no longer receive communications from an organization via email and therefore unsubscribe. These are usually tallied with the email campaign through which they clicked the unsubscribe link.

Complaints

Complaint rate is the amount of subscribers who have reported an email as spam or phishing. While some elements can have a more immediate impact on reputation than others, like complaint rates, all of the elements advised above help to paint a picture of the subscribers’ experience as a whole with a sender’s content and marketing practices.

A trend of negative metrics growing towards the advised thresholds can be a forewarning of growing negative experiences with sending practices. To help protect your sending reputation, monitor for poor engagement metrics before they grow to a problematic level and implement corrections quickly.

3. Bad subscriber acquisition practices

Subscriber acquisition refers to the process by which subscribers are added to your sending audiences. How a marketer collects subscriber addresses can make or break their eventual sender reputation.

Good list acquisition practices look like this:

• Signup forms that outline explicitly what content a subscriber is signing up for

• A checkbox for marketing content in a purchase process is set unchecked by default

• Some form of CAPTCHA security to protect signup sources

Poor list acquisition practices look like this:

• Content gates that require an email address to see a blog, etc.

• Giveaway gates that require an email address to enter to win

Bad list acquisition practices look like this:

• Purchasing lists of addresses

• Scraping addresses off of the internet, e.g. from a conference attendee list

• Referral benefit programs requesting subscribers to provide a friend/colleague's address for discounts, etc.

• Acquiring through opt-out instead of opt-in practices (see Ch. 4)

Following best subscriber acquisition practices is about using methods that give the subscriber full visibility and autonomy in the subscribing experience, before a single email is sent.

4. Poor list management

List management refers to the process of organizing, auditing, and cleaning out subscribers whose inactivity will lead to poor sender reputation.

If you don’t continually clean your email lists, you will repeatedly send emails to old or unengaged subscribers. These will contribute to ongoing negative engagements, which will harm your sender reputation and cause you to miss the inbox.

To mailbox providers, a passive recipient’s permission to send is eventually revoked by inactivity. As a sender, aligning with that perspective will mean you are aligning with the mailbox provider’s idea of what makes a good sender.

Permission to send should have an expiration date. At Ortto, permission to send ends at 12 months of no engagement for an address. Good list management practices should include a re-engagement attempt and sunsetting of such addresses before they reach the 12-month mark. Poor list management would be little to no maintenance of this kind so that lists of unengaged addresses grow and grow until the majority of the audience is unengaged.

5. Spammy send practices

The old ways of close-your-eyes-and-just-send-to-everyone email marketing practices have not only been legacied out but are now considered forms of “spammy send practices.”

These practices look like this:

• Unfocused content: Filling an email with every ounce of content possible without awareness of subscriber preference or interest.

• All-or-nothing list setup: Sending all content types to the entire subscriber database instead of separating each content type with its own list.

• Generalized approach: Not utilizing personalization tags or dynamic content that elevates items or information that the subscriber has shown previous interest in.

• Unregulated send frequency: Sending too frequently or too sporadically.

• Unresponsive send strategies: Creating email marketing strategies that do not take into account response metrics from previous campaigns.

6. Poor ramp-up experience

Because of the amount of malicious activity that occurs within email, systems rely on tools that identify good senders from bad by attributing reputation to certain technical elements, like the IP address or the domain attributed to the sent email.

Making a sudden change without slowly ramping up your sending volume, using either new IPs or domains that are lacking reputation, or new-to-you IPs/domains not usually associated with your emails, can cause spam filters to become suspicious and trigger more easily.

Also, not alerting your subscribers of the change before it occurs can either cause a lack of trust (if you start sending from a new email address they don’t recognize), or a lack of proactive searching (should the change cause extra filtering). People need a heads-up and systems need time to evaluate and recognize the new change.

7. Bad links & URL link shorteners

Links have become one of the greatest vulnerabilities around email, especially due to the success rate of phishing, spoofing, and the social engineering tactics that often accompany such activities.

Malicious actors have so staunchly abused link shorteners like bit.ly and file-download links like PDFs, that security systems are more likely to outright reject an email if it feels the link is too unsafe to let through.

These types of links hide the quality of the content behind them so well that even good senders that include them in content can experience sudden deliverability issues.

8. Bad image-to-text ratio

Sending emails that are made up of only an image or multiple images can look suspicious to security systems that are not able to parse the information being provided in said images (at least not yet). Malicious actors use this tactic to hide spoofing as well as other abusive activities.

Security systems also understand there are many human elements possibly missing to cause a warning, such as a lack of alternate text for visually-limited users or those with image-blockers turned on.

This is why the concept of an image-to-text ratio in deliverability is important, and how a balance of the two can help protect from a misapplied filtering experience.

Ortto users can easily design emails that are clear, easy to read, and have a good image-to-text ratio using the drag-and-drop email editor.

Email templates

Email marketing templates

Use templates

9. Lengthy content

As is the case with any marketing medium, content that is too long is not easily digestible and may be off-putting for readers.

Beyond that, there are also technical limitations that can affect deliverability for scenarios with lengthy content.

Some mailbox providers like Google have a cut-off point where they don’t load the lower half of the email content unless the reader clicks a link requesting to view it. This can affect open rates, as the image pixel used to identify an open is in the lower portion of most providers’ emails, so if it is cut off it won’t show an open.

Another thing to note is that if an email’s content is too big of a file size, many providers will outright block/bounce that email so that they don’t have to hold that amount of storage (remember, when sending bulk, they have to store that huge email in duplicate for all of those subscribers hosted by them).

Ultimately, there are both human and technical reasons to avoid long bulky email content.

10. Technical issues with ISPs

If you’re sending to high-risk providers like banks and government bodies, in most cases you can’t just hit send and deliver easily.

Because of the vulnerability and important information at stake on their end, such mailbox owners have to create some of the most stringent security limitations around external mail being received by them.

Sometimes it’s as easy as requesting they add your sending address/IP to their internal allowlist or it could require an end-to-end encrypted delivery connection like transport layer security (TLS), which is not defaulted on by most providers.

The message is clear: Not taking the time to understand your audience’s technical needs can lead to an inability to deliver a single message to them.

Key takeaway

As email has evolved, the list of bad practices has grown, which can seem daunting. However, rather than creating your email strategy based on a list of 'don'ts', it is better to focus on 'do's'. In Chapter 4, we provide not only a list of action items, but recommendations of how to shift your mindset when it comes to deliverability, so you can instinctively make better decisions now and in the future.

How to improve email deliverability

Think of email deliverability as a formula: more positive signals (opens, clicks) than negative signals (unsubscribes, ‘mark as spam’) will improve inbox placement and increase brand visibility and engagement.

Ortto’s Head of Email Deliverability, Travis Hazlewood asks that marketers, above all, provide an email experience that’s “secure, transparent, engaging, and respectful.” Doing so will give them the best chance of earning inbox.

There are three main pillars of deliverability: Get consent, engage meaningfully, and be human. Let’s explore each of these.

1. Get consent

Active subscriber consent is the foundation of strong email deliverability. How you gather your subscribers and empower them to control their subscription preferences can make or break your deliverability experience.

If you are emailing people who do not want to be contacted by you, your open rate will be low and your bounce rates and unsubscribes will soar. This will affect your domain reputation and, in turn, your deliverability. Needless to say, it’ll also affect your brand reputation.

Ensure that you are clearly communicating how subscribers can opt into your marketing emails and retain control over their preferences, and empower them to make decisions about what they want to receive. As an email sender, you must honor their preferences to maintain trust and build a list of engaged subscribers. Do this by employing opt-in rather than opt-out subscriber acquisition practices.

Implement explicit opt-in practices

Before you put somebody’s email address into a subscriber bucket, ask yourself: did they explicitly opt-in to receive this type of email communication from me?

Signup sources should clearly outline the type of content being opted into and those expectations should be honored.

A great way to confirm this experience is to promptly send the subscriber a Welcome Email to request their confirmation of the signup preferences.

Below are examples of Welcome Emails where the recipient is asked to complete one action: confirm their subscription.

Welcome email examples

Source: Really good emails

Template

Welcome email

Use this template

Another scenario to consider: A customer may have purchased a product or service and in order to complete the purchase had to provide their email address. This doesn’t necessarily mean they want to receive marketing emails from you. Ask them to tick a box that specifies they want to hear from you and then ask them to confirm that they opt in.

When someone does unsubscribe from an email list, acknowledge their preference with an email. See below.

Source: Really good emails

While the above takes care of organic, human activity, there are malicious actors out there who abuse people’s mailboxes by finding vulnerable signup forms and adding their addresses unknowingly. Because of this, you should also secure your forms with some version of CAPTCHA to prevent this type of abuse. This will help to ensure your email lists are high-quality and secure.

Don’t utilize gating for subscriber acquisition

While acquiring addresses through forms for gated content or one-time offers can result in a large number of subscribers, these subscribers may only be interested in that one opportunity and their future email engagement may be little to nothing. Examples of gated forms:

• Content gateways for blog posts, ebooks, whitepapers, or site access (when not a part of a paid-subscription model)

• Giveaways

Gated forms can also encourage users to input secondary or temporary addresses, resulting in un-opens or bounces, which can negatively impact deliverability. So, when subscribers give consent freely, without going through gating, you will build higher-quality subscriber lists.

Incorporate an email preference center for various content and communication channels

Unsubscribe accessibility is paramount to good email marketing – and in turn deliverability. Having an email preference center where subscribers can manage the communication and content they receive across various channels is crucial. It lowers the chance that subscribers become frustrated or disgruntled and mark your emails as spam – the proverbial kiss of death for deliverability.

A preference center allows subscribers to self-serve. You must then honor their wishes and remove them from any lists they don’t want to be in. If you’re an Ortto customer, you can easily choose which audiences appear in your email preference center as a subscription. Just go to the audience, click ‘Edit’ under ‘Setup’, and check the box. From there, you will be able to assign the audience a public name and description.

Remember: an unsubscribe is better than a complaint.

A good example is an email that provides clear subscription management instructions is from the media platform Mashable. It reminds readers that they can manage their subscription preferences to suit their interests. The instructions are clear and descriptive, which gives a positive signal to readers that they are respected. See below.

Employ list maintenance practices

Subscriber lifecycles are not identical, but we can break down some general, rule-of-thumb guidelines to help give a good idea of how to protect and honor a subscriber’s experience.

Studies vary, but it is generally understood that a subscriber’s most convertible timeframe is within the first 30-90 days of subscription. After 90 days of no engagement (e.g. an open or a click), they are in danger of being difficult to re-convert, making them a liability to your email deliverability. But let’s be honest, people are forgetful and rarely proactive when it comes to their subscription preferences.

The optimum time to re-engage dormant subscribers is between the 90-180 day mark using win-back email campaigns. After that, their lack of engagement will continue to wear on your reputation and may cause them to become annoyed and respond negatively to your emails (especially if they have not been inboxing for a while but suddenly are, so they think they are being spammed).

Tactics to win back inactive subscribers include:

• Use humor to get their attention: Appealing to them on a more personal level can help them to see your company in a new light.

• Update them about product/company changes: Maybe they were dissatisfied with certain product features or your ways of doing things, so be sure to let them know what you’re offering before cutting contact.

• Offer incentives: If all else fails, try to incentivize them to keep interacting with your brand. For example, you can offer them a free coffee if they reply to your email newsletter with feedback or content requests.

You may also ramp down the email frequency for subscribers showing waning interest. This way, you’re being careful not to bombard them with content that may push them away – or push them to ‘mark as spam’.

Having a regular re-engagement and sunset process of older, unengaged subscribers (6-12 months unengaged) is a great way to both honor your audience’s passive preference and retain a strong sender reputation with mailbox providers.

Losing the interest of subscribers is frustrating, but inevitable. There are many reasons why this may be the case: a subscriber’s interests may change; they are dissatisfied with the emails they are receiving; they subscribed to fulfill a need that has since been met, or they want to de-clutter their inbox.

It’s important to accept that it’s okay to let go of inactive subscribers. Relationships run their course, and if you can’t re-spark their interest in your company and offering, it’s better to let them go.

2. Engage meaningfully

Meaningful engagement is another cornerstone of good deliverability. Work with your subscribers to identify their desires and expectations, as this will fuel engagement and subsequently improve deliverability. A big component of engaging meaningfully is to personalize content.

This involves:

• Personalizing email subject lines

• Segmenting audience lists and sending only relevant content

• Ensuring content is highly focused and timely

• Utilizing A/B testing to identify effective approaches

• Providing a robust preference center experience for subscribers to set up-to-date preferences

Senders should also respect recipients by providing unsubscribe accessibility:

• Elevate accessibility of the Unsubscribe button so that people choose it over the Spam button

• Utilize two-click unsubscribe

• Remember: An Unsubscribe is much better than a complaint

Between passive methods like adjusting strategies based on subscriber engagement, to active methods like subscribers updating their preferences and contact fields, there are so many ways that a targeted, meaningful approach to your marketing content can be achieved.

Ortto makes providing a personalized experience easy and accessible for marketers. Ortto users can benefit from the following:

• Highly versatile segmentation experience

• Subject line A/B testing & AI recommendations

• Dynamic content tags based on custom field data

• Highly responsive Journey/Playbook pathways based on custom field data and subscriber behavior

3. Be human

The final building block is simple but often overlooked: be human. Be human in the way you speak to your subscribers; in the way you honor their preferences, and in the way you earn their trust.

The goal is to be as authentic and as personal as possible in a way that provides value and, in turn, earns the subscriber’s attention. Earn is the keyword. We know that the average person gets over 100 emails per day, and likely doesn’t have the time or desire to sift through them all. So, to grab their attention and amp up your email open rates and click-through rates, you should appeal to your subscribers’ interests and make them feel seen. The best way to do this is through engaging, natural language.

When your subscribers feel respected, they will not only regularly engage with your content, but will actively seek it out. And, ultimately, this is what email marketing is about – building brand awareness and a loyal customer base to gain preference over competitors.