The expression is also used to describe your relative success at getting email delivered. That's why you hear people talk about "improving" their email deliverability, which means taking action to ensure more emails reach the people who signed up for them.
If you're new to email marketing, you might wonder just what issues there could be around delivery. After all, you write an email, you put in the recipient's email address, you click "send", and you expect it to land in front of that recipient a moment or two later.
Unfortunately, when you send marketing email that goes out to dozens, hundreds, thousands or millions of recipients, not all of those recipients are going to get your email. In fact, it's not unusual for a good 10% to miss out on your message.
Nobody can click on a link in an email they never see. Which is why deliverability is important. The worse your email deliverability, the less successful your email marketing efforts.
So why don't all the emails you send land at the desired destination? There are two main reasons: bounces and anti-spam measures.
You can think of a bounce as an email that is "returned to sender." The email gets sent off OK, but for some technical reason it can't get through to the recipient email address. The email infrastructure recognizes the delivery problem and normally informs the sender that the email has not got through by sending back an informative email (the bounce message).
There are many reasons why an email might "bounce", but they generally fall into two camps.
The first group of reasons is where there is some permanent technical problem with the recipient's address. For example, the email address you're sending to just does not exist. If you tried to send email to mark@aol, it would bounce (just like the original email referenced in the above bounce message.)
There is no mark@aol. There might be a firstname.lastname@example.org, but the email systems we use can't think for themselves. They just see a bad address and bounce the email.
If people submit their email address to you so you can send them direct email marketing emails, you might rightly ask how you'd ever end up with a non-existent address in your list.
Fact is, non-existent addresses are inevitable. For example, people change jobs and their old email address gets deleted. Addresses in your email list "go bad" over time. A certain level of hard bounces (as these permanent address problems are often called) is to be expected.
The second group of reasons for a bounce is where there is some temporary technical problem with delivering the email. One reason for a temporary problem is where there is a dodgy connection somewhere along the line. For example, if the website you're currently reading went offline for a few hours, emails sent to me would not get through.
These temporary problems (often called soft bounces) are handled in a variety of ways by the email system, depending on the nature of the problem and the services being used to send and deliver the email.
Often, the system keeps hold of your message and tries to send it again later. Sometimes the bounce message will tell you this. Sometimes you might get a bounce message several days after you sent out the email, telling you that the system has just given up trying to deliver to a certain address. Sometimes you might get no bounce message at all.
Bounces are a science unto themselves, but for now it's enough to know that technical difficulties can interfere with delivery of email.
2. Anti-spam measures
Anti-spam measures are where the system receiving the email at the recipient's end deliberately interferes with delivery of your email.
Unwanted spam emails are a scourge on the Internet, and the email marketing companies which provide the services, software and infrastructure for people to use email go to great lengths to prevent spam emails getting through to people. So there are various mechanisms in place for identifying email as spam.
Any email so identified is either deleted undelivered or sent through to the recipient's junk/spam folder, rather than to their inbox. So the recipient never sees the spam email...either because it was never delivered in the first place or because it disappeared into that junk email folder.
The problem for email marketers is threefold.
First, the anti-spam mechanisms in place are not perfect. Sometimes they label a perfectly normal email as spam. That's the so-called false positive problem, where perfectly legitimate marketing email gets caught up in the anti-spam net.
That's why you can't assume that just because you don't spam, you won't have delivery problems due to anti-spam measures.
Second, the number of different anti-spam mechanisms out there is enormous. Each email service may take a different approach to controlling spam. This makes it difficult for marketers to create and send out legitimate marketing emails that take account of anti-spam mechanisms.
Third, when your email gets called spam and dealt with accordingly, you very rarely get any feedback. You rarely get a bounce message like you would if you were trying to send email to a non-existent address. So it's not always easy to pinpoint the cause of any particular delivery problems. Or even to know if you have one.
You can begin to see why deliverability is such a big issue among email marketers. Fortunately, there are things you can do as a sender of marketing emails to ensure as many get through as possible.
The nice thing about delivery problems due to bounces is that you know about them. You get bounce messages that usually (but not always) contain information that explains the problem. So you can take the appropriate action.
If you use an email marketing service to send out your emails, the reports they give you should include information about bounces.
This information tells the sender to take non-existent addresses ("user unknown") off her list. And shows her to keep an eye on those addresses that have connection problems ("timed out".) If those same addresses continue to bounce when she sends emails to them at a later stage, she'll need to take them off her address list, too.
Many email marketing services build this bounce management concept into their system. If an address produces a soft bounce for X emails in a row, then it's automatically removed from future mailings.
It's important to "clean up" your address list like this because bounces are more than just an inconvenience.
Repeatedly sending email to an address that doesn't exist is something spammers do. So such behavior can result in one more tick on the "is this spam?" checklist used by email systems when deciding whether to deliver your email or not. Increasingly, these systems are restricting the delivery of emails from senders who produce too many bounces.
Managing bounces comes under the heading of "list hygiene."
Coping with anti-spam measures is another issue entirely. And this is a hot and complex topic in email marketing. But let me offer some words of reassurance...
Anti-spam measures are there to stop spam. They're not there to stop legitimate marketing email. In fact, the anti-spam fraternity and marketers are on the same side. Neither want spam to get through and neither want normal emails to get blocked or filtered out from the delivery flow.
The anti-spam groups dislike spam because it uses up infrastructural resources and annoys the heck out of people.
Marketers dislike spam because it clutters up inboxes and casts a bad light on email as a whole. And because it forces the email community to put up delivery hurdles and blocks that legitimate emails get caught in too.
There are lots of clever practices to ensure your emails are not labelled and rejected as spam. But the basic message is this...you can go a long way to maintaining good deliverability by sticking to this basic principle:
Send useful, relevant emails to people who have explicitly requested them.
Spammers send email to people who don't want them...so don't do that.
The emails that spammers send contain nothing useful...so don't do that.
Good email deliverability comes from bounce management and permission-based email marketing. Permission-based means ensuring that what you send and when you send it reflects not just your own business needs and wishes, but the needs and wishes of the recipient. Good luck!