Why Inbox Provider Don’t Approve of Email Validation and Email Tester Services

Most (but not all) email tester and email list cleaning and validation services are generally frowned on by many (if not most) inbox providers and ISPs, and many consider their use to be a sign that you may be a spammer. The rise of list cleaning (also known as “list hygiene”) and email tester services, by which we mean email address validation and verification services, has tracked in tandem with the rise of new ways to detect spamming activities, including adding email addresses to mailing lists without consent.

It’s this last bit, the “adding email addresses to a mailing list without consent” that is the sticking point, and it is that activity which list hygiene services are, for the most part, intended to facilitate. Which is why they are disdained by the email receiving industries (inbox providers, ISPs, and spam filtering services). There’s a reason that they are called “list cleaning” services; and if you are building your mailing list with consent then your list won’t be dirty and need cleaning. Note that it’s important to distinguish these services that offer just these list “hygiene” services, and those who help you to not only clean up your email list, but also to make sure that you are following best practices.

In case you’re not familiar with email address validation services, here’s basically how they work: you upload your email list to their server. They then go through all of the email addresses on your list, removing certain types of email addresses (such as addresses that start with ‘info’, ‘no-reply’, and ‘support’), and removing known spam traps. Then they test the rest of the email addresses by creating an SMTP transaction for each one to see if the receiving mail server acknowledges the existence of that email address. This last step is to remove email addresses which will bounce when you email your list, because lots of bounced email addresses is also a sign of likely spam.
Here’s an example:

Let’s say you are going to use Acme Email Validation Services. So you sign up with Acme, and then you upload your mailing list to them. They know that “sp******@ex*****.com” is a spamtrap, so they remove it from your list. It’s important to note here that the list cleaning services only know about the spam traps that they know about; there are a whole lot of spam traps that they don’t know about, and that is intentional on the part of mailbox providers, ISPs, and even us.

Once they get rid of the spam traps that they know about, they move on to role accounts. For example,
they know that “su*****@ex*****.org” is likely to complain about you spamming them because it’s a support address, so they remove that too. After cleaning the list, what’s left is a list of email addresses that are theoretically valid, however some of them may be really old and no longer in use, so that if you email one of those addresses it will bounce. Let’s say that these email addresses include jo*@ex*****.io, be***@ex*****.net, and jo********@an************.com.

Acme’s mail server will attempt to connect to each of example.io, example.net, and anotherexample.com, via SMTP (which stands for “simple mail transfer protocol” and is the most widely used protocol for sending email from one computer to another, but that’s not important right now). The way it basically works is this, using the jo*@ex*****.io example:

Acme’s acme.com mail server connects, via SMTP, to example.io. Once connected, it announces that it has an email message for jo*@ex*****.io. (It’s lying, it doesn’t have an email message for Joe, and it intends to disconnect as soon as it gets the info it wants.)

Now example.io will respond either by saying that yes, there is an account called “joe” at example.io, and wait for the next instruction (which never comes because Acme doesn’t really have email for Joe), or it will tell acme.com that there is no such user at example.io. (There are actually other possible responses but those too are not important right now.)

Either way, Acme now has the information it needs to either leave jo*@ex*****.io on your mailing list, or to remove it.

As you can see, all of these steps by Acme are designed to help make you look less like a spammer. Which, in the eyes of the inbox providers, you probably are. Because you wouldn’t need a list washing service if you were only sending email to people who had asked for it. You wouldn’t need your mailing list cleansed if it was already clean because you weren’t adding email addresses to it without their consent.

Do you see the problem?

Not only that, but the act of creating SMTP connections for the sole purpose of testing an email address is considered abusive by the majority of email receivers (inbox providers and other ISPs). It’s tying up their resources, and using their bandwidth.

Most in the email receiving industries have the view that there is one, and only one, situation in which it’s appropriate to use a list cleaning service, and that is when you have an old mailing list, built with the consent of all of the email addresses on the list, but it hasn’t been mailed to in a very long time. In that situation it’s possible that some of the email addresses on the list, even though they gave you consent at the time, are no longer valid. In such a case you are going to conduct a “re-engagement campaign”. If that is your situation please read our recommendations for How to Revive, Warm Up, and Re-Engage an Old Mailing List without Getting Into Trouble.