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Are subscribers seeing your email? It is an important and often overlooked question. Deliverability monitoring is the answer.
Before assessing email engagement and ROI, marketers need to ensure their campaigns are making it to recipient inboxes. Deliverability measures their ability to do just that. A combination of factors influence this metric, including delivery rate, subscriber engagement and IP reputation.
What does Delivery Rate mean?
Delivery rate is a measure of a sender’s emails being successfully delivered to an internet service provider (ISP). If an email service provider (ESP) attempts to deliver an email to an ISP, and the ISP accepts the email without rejecting it (which would be considered a bounce), then the ESP considers the email to have been delivered. In other words, if a campaign is sent to 100,000 recipients, and 1,000 of those emails are bounced or rejected by the recipient system, that email had a delivery rate of 99%.
Sounds great, right? But what is happening to that email after an ISP accepts it? Are they placing the email in a spam folder? Are they deciding to not show it to the recipient at all? Those factors are measured by a metric called inbox placement.
What does Inbox Placement mean?
Inbox placement is a measure of how often email is delivered to the subscribers inbox, rather than being held or placed in a spam folder. It is a far more useful metric than delivery rate, and a better indicator of how much email is being seen by subscribers. Delivery rate simply means that the email was accepted by an ISP, but inbox placement measures what they do with the email after accepting it.
Return Path estimates that only 82% of campaigns in the United States made it to the inbox. This means that approximately 1 in 6 emails are either being held, marked as spam or otherwise not appearing in the recipient inbox.
What are the factors that influence deliverability?
Deliverability is derived from a variety of factors that carry different weights, which affect how they are scored by different mail providers. ISPs and filtering companies don’t typically publicize the exact algorithm used to sort and score email, but there are set of commonly accepted settings and metrics that senders should consider:
Email Infrastructure
These settings are often managed by the ESP or a sender’s internal IT department. They include DNS records to support things like DKIM, SPF and DMARC. These entries help ISPs confirm that the sender is authentic and allowed to send email on behalf of the sending domain. They help to filter out spoofed email, phishing campaigns and spam. Emails that fail checks for DKIM and SPF are more likely to be marked as spam by ISPs.
Email Volume
Consistent email volume is an important factor in deliverability. If a sender deploys 500 emails one week, 2 million the following week, and 1,000 the week after, they have a much higher likelihood of being identified as spam. This behavior is common among senders of unsolicited email, as they don’t have a true subscriber base. Make an effort to have consistent volume over time to avoid triggering any alarms at ISPs.
Content and Code
There was a time when using the word FREE in a subject line could cause an email to be marked as spam. That type of content monitoring isn’t really a concern today, but ensuring that your emails have clear, valid html, render on mobile devices, and don’t include any scripts or other dangerous code snippets is an important step. Consider using tools like Litmus to help validate campaigns.
Bounce and Complaint Rates
As an email marketer, it’s important to understand the distinction between hard bounces, soft bounces, and spam complaints. Hard bounces occur when you send an email to an address that doesn’t exist. Soft bounces occur when an address exists, but is unable to receive email at that specific time, perhaps due to a full mailbox or some other temporary condition. Spam complaints happen when a recipient marks an email as spam in their email provider, or reports it to a third party blacklist or abuse group.
Hard bounce rates should be less than .5% and spam and complaint rates should be less than .02% for email campaigns. These factors are weighed when ISPs decide how to score and route email. If a sender is constantly bouncing large numbers of emails, or seeing large numbers of spam complaints, their campaigns are likely to be considered spam or to be rejected outright by the recipient system.
If a sender is seeing a lot of spam issues, they should review their email signup process, and consider using a third-party validation tool such as ZeroBounce. Validation tools will help to determine if a new email signup is indeed a valid address, before trying to send it a message. If they are experiencing a high number of complaints, it’s a good idea to review the opt-out process to ensure that it is functioning properly, and that user preferences are being honored with each campaign.
Engagement
Engagement is the single most important factor affecting deliverability. ISPs closely monitor how recipients engage with email, and react accordingly. If a sender routinely has low open rates, few clicks, and high unsubscribes, for instance, it’s quite likely that an ISP will begin to mark all of their email as spam.
This level of engagement monitoring makes it crucial for senders to optimize engagement rates by sending timely and relevant content, managing customer preferences, and suppressing recipients who aren’t engaging with email.
In an effort to optimize open rates, senders should consider suppressing subscribers who have not engaged over a period of time — perhaps 1 or 2 years, depending on your business and frequency of communication with subscribers. Also, segmenting your list and utilizing personalization within emails will help to increase engagement and decrease unsubscribe and complaint rates by showing relevant content to your audience.
Sender Reputation
Many of these deliverability factors are monitored continuously by ISPs, and used to create a sender score or sender reputation. These scores are typically applied to the sending IP address, but can also be applied to sending domains. If a sender has a low score based on past performance, they are very likely to be marked as spam and bulked.
Sender reputation can be determined by the following factors:
- Email volume
- Spam and complaint rates
- Bounce rates
- Unsubscribe rates
- Spam traps
- Inclusion on third party blacklists
- Engagement rates (opens, clicks, forwards)
If a sender has a dedicated IP address, meaning that they are the only ones sending email from that IP, the reputation is entirely their responsibility. They should take care to properly warm a new IP by slowly increasing the volume of email being sent over time, and closely monitor all of the factors described above.
If a sender is using a shared IP address, they can be affected by any other senders using that same IP. This is a common configuration with ESPs such as Mailchimp, Hubspot and Constant Contact, and even with larger ESPs for customers with lower mail volume. If a sender isn’t sure whether they’re on a shared or dedicated IP, it’s most likely shared. It’s important that the ESP hold senders accountable to its policies, and disable sending for anyone not following best practices, in order to preserve IP reputation for everyone in the IP pool.
To get an idea of the reputation for any particular IP, check Return Path’s Sender Score.
Summary
Measuring and monitoring inbox placement is critical for marketers. The best way to verify that messages are being delivered correctly is to use a third party monitoring tool, such as Everest from Validity. The tool provides seed addresses to include in outbound campaigns, and then monitors and measures the placement of emails sent to those addresses. They serve as a proxy for the performance for your actual subscriber emails.
The success of an email program depends on arriving in the inbox. If emails aren’t seen, they can’t be opened, can’t generate clicks, and can’t drive revenue. Get and stay in the inbox by having a sound strategy, a knowledgeable email team, and sending relevant, engaging content.
