The Long & Winding Road to the Email Inbox
Deliverability
Email deliverability at first glance doesn’t seem to be a complex topic, right? It’s basically your likeliness
to reach the inbox as opposed to landing in the spam or junk folder, or being rejected all together.
Sounds basic enough, but when you dig down to what it takes to make it to the inbox, there is a lot more
to it.
As it turns out, the path to the inbox is a long and winding road, but can easily be broken down into
these 5 elements:
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5.
Blacklist Check
Authentication
Reputation
Content Filtering
Engagement
Blacklist Check
Blacklists are 3rd party spam filters that ISPs subscribe to. Spam filters identify emails first by the IP
address, then by the domain of the sender. Having the mail server you use for sending your emails on
one or more blacklists may cause that your messages will never reach their recipients. There are several
blacklists and they all have their own criteria for accepting inbound mail and can all impact your ability
to get to the inbox.
How does it work? When a blacklisted mail server try’s to send an email, the target mail server declines
the message and could even block the initial network connection from the blacklisted address, making it
impossible to deliver the email. Even legitimate mail servers can end up on blacklists. Using a blacklist
checker upon having any suspicion of having a blacklisted server, will save you time as well as prevent
potential problems as recovering from being blacklisted is painful. There are plenty of online ‘blacklist
check’ tools that you can use to determine if you are on a blacklist, by simply providing your server IP
address or your domain.
Authentication
Email authentication confirms that the identity of who is sending the email, is in fact the source that is
stated as sending the email message. Sender ID and SPF are IP based authentication methods while
Domain Keys and DKIM is a cryptographic based authentication. It’s important for the ISP to validate the
email sender in order to fight fraud or forgery and email authentication automates and simplifies this
process.
Email authentication and authorization systems have been part of email delivery since SPAM existed and
how to handle when a message fails has become a complex question to answer. Mandatory Email
Authentication and What It Means for Marketers is a good article that talks about recent changes and
the importance of making sure you have your authentication in order.
Reputation
Your reputation as an email sender has become more and more important and controls access to the
inbox. Similar to a credit score it is how ISPs view you and your email practices over time. There are
several email reputation monitoring tools, such as Cisco’s SenderBase and Return Path’s Sender Score.
This reputation score indicates to ISPs if you are a trustworthy email source. How does it determine if
you are to be trusted as a email sender? Sender Score for example, uses an algorithm based on metrics
that discerns legitimate email from spam. A low score means low email delivery to the inbox, while
higher scores will get more of your email in the inbox. Factors that influence your reputation include:
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Permanence and IP address stability
Spam complaints
Spam trap violations (pristine vs. recycled)
Blacklists
Hard bounces/unknown user rate
Volume and consistency of mailings
Sender rejected/accepted rate
External reputation
Content Filtering
Content filtering is still on the ‘path to the inbox’, but certainly much less important than it used to be.
Content filtering is analyzing the email content itself. What do the spam filters look for? It starts with the
email header, what the from line says and the subject line. It also looks at your HTML source /
anomalies, plain text content, hidden content and links in the email.
There are free online tools like Email Spam Test or ISnotSPAM, that can help you find some of these
elements that might trigger content spam flags. Even though you may past these content checkers,
don’t forget other variables that are monitored like emails that contain just a single image or emails with
attachments.
Engagement
ISPs use heuristics to refine their systems by monitoring what is going on in their users mailboxes. They
will look at what gets opened, what is deleted before opening, what is being clicked and what does the
historical behavior look like. In many cases bulk delivery decisions are based on the user’s behavior.
Thus, monitoring your email recipient’s engagement with your communications, not just to see what the
metrics are but rather to scrutinize trends, is key. In other words, it’s not just looking at industry email
trends and benchmarks, but benchmark yourself first and foremost in order to monitor trends over
time.
Food for Thought
Even though email deliverability is more complex that just hitting send, we do have the ability to
influence getting it into the inbox. You don’t have to make big dramatic changes, you can start with
incremental improvement.
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Ensure you have process in place to monitor email engagement and sender score across your
IPs.
Monitor your list of users and manage your database – purge inactives and hard bounces,
reconfirm that your users want to receive the information you re sending.
Stay away from email practices that produce low engagement, i.e. sending the same message to
everyone in your database, what’s typically referred to as batch and blast or spray and pray.
Create ‘welcome programs’ when they register for newsletters or to receive information, so
your users know what frequency and types of emails you will be sending
Without a doubt focusing on deliverability will ensure more of your email will make its way to the inbox
and less will end up in junk mail and spam folders.
What have you done to improve email engagement and deliverability and what impact has it had?
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