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The email that doesn’t make it to the inbox is like the proverbial tree that falls in the forest with nobody around to hear it – what’s the point?

One of the eternal quests of email marketers is to stay out of the spam folder. Still, deliverability, while at the heart of all email communication, is often one of those priorities that gets buried by our focus on measurements like list growth and open rates.

Times have also changed for how email clients and internet service providers decide what does and doesn’t get into the inbox. You may remember the First Age of Deliverability, the Wild West, no-rules era of email — or the Second Age, which centered around the “report as spam” button.

As email marketing expert Chad White describes, we are currently in the more nuanced, complex “Third Age of Email Deliverability,” where filtering decisions take into account both individual and collective engagement. That means the same message from a company following all the deliverability best practices can get stuck in the spam folder in one person’s email and waltz into the main inbox for another.

So how do you optimize deliverability and what do you do when you find your labored-over emails plunge into spam purgatory? I chatted with our email and support expert Diana Potter to find out.

Email Deliverability 101 - A Review

There may be a number of best practice tips floating out there, but just 2 basic ground rules of deliverability.

Set up email authentication.

Authentication isn’t so much about reputation-building (which is tied to your domain) but trust.

Most email providers look at authentication, because they need to know if they can trust that a sender is who they say they are. It’s like checking a Social Security number or passport to prove your identity. Failure to set up your email authentication paves the way for delivery problems, because the lack of trustworthy evidence will cause email providers to scrutinize and filter emails more severely.

(Read more about authentication in our overview and links to instructions for some commonly used hosts). sample authentication

Be relevant.

The very definition of deliverability involves reaching someone, encompassing not just mere broadcast but also receipt. So email success is not about sheer numbers but quality connections.

Maintain a quality email list by sending only to people who have opted in and given you permission. Regularly check the health of your list, and prune people who haven’t opened in ages.

Create quality content for your list and send information relevant to their interests. That means more segmentation, knowing your audience, and staying away from blanket email “blasts”.

Why is My Email Being Sent to Spam?

Seeing your emails land in spam can provoke the kind of rattling panic or anxiety that’s made worse by not really knowing how to fix the situation. Let’s look at how email providers make those filtering decisions.

In this Third Age of Deliverability, email providers look at a wide variety of metrics. Still, they largely focus on engagement and individual domain reputation, which is how users are treating emails sent from your domain (rather than just the IP) and your email contents. (If you’re using high-quality ESPs, including Customer.io, you don’t have to worry much about managing IPs.)

Each email client also has its own spam-filtering rules (which aren’t publicized, in order to stay ahead of actual spammers). Nonetheless, personal filtering decisions by users do factor into overall spam filtering. This includes steps like users not opening emails, users deleting emails without opening, or even how users treat similar emails.

Here’s how Aaron Beashel from Campaign Monitor summarizes 7 signals used to determine engagement, both on an individual and global level:

The impact of a user reporting an email with a “mark as spam”-type button will vary, depending on whether providers have “feedback loops” that collect information on spam complaints and forward them on to many established ESPs for reporting and processing. (In Customer.io, we suppress future emails based on such direct spam actions.) Hotmail (now Outlook.com) and AOL, for example, have such feedback loops. Gmail treats individual spam reports differently, so you might not see the same kind of direct impact from Gmailer’s spam reports. Customer.io sample report

Many people ask us if sending emails from personal addresses, as opposed to more generic addresses — such as “email@example.com” versus “firstname.lastname@example.org” — harms deliverability. If anything, this tactic will improve it, since people are more likely to open these personal-looking emails(as long as they recognize your name). Whatever you can do to remember to be human increases engagement and thus decreases the likelihood of spam-filtering.

How to Test Your Emails for Spam Issues

Watch for drops in open rates, emails actually landing in spam folders, or a spam rate higher than the average .02%. These are signs to check for spam filtering issues.

Run manual and automated tests.

For manual testing, send your test emails to a variety of email provider types, such as Gmail, Outlook, and Yahoo. Use multiple accounts for each (since filtering can be so personalized) and see what happens.

To run full, automated spam tests, we recommend tools like Litmus or Email on Acid, which both provide visual previews and spam checks for ISPs and webmail providers, as well as corporate filters. sample Litmus test

Locate the issue.

Send any email you see filtered to multiple addresses at one provider to see if it’s an issue localized to one email address, client, or everywhere. If you observe spam filtering happening in specific email clients — focus your tests there. For example, if you only see spam filtering at Gmail, it’s most likely a Gmail issue — whether it’s one Gmail account or Gmail not accepting your content.

Test your content.

If you see spam filtering across clients, focus on testing your content. Here’s how you can hone in the problematic sections:

Figuring out content failures is a trial-and-error process, but you can generally narrow it down by doing this type of systematic sweep testing.

If spam-filtering isn’t concentrated in one client, it could be an engagement issue. Fixing engagement problems can take much longer, but getting people to whitelist your emails by adding you to their address book and slowly getting more opens and clicks by providing relevant content will help over time.

Have any burning questions about deliverability or other email issues? Send us an email or tweet us!

Photo: Freezelight/Flickr

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