How To Verify Email Addresses Validity?

Why Do You Need To Verify if it is an Active Email Address?

Many email marketers think that there is no need for an active email verification process. They assume that they can periodically clean up their lists based on bounces or even just leave them as is.

After all, they wonder, what harm is a bad email address doing? The reality is that email verification can greatly benefit your email marketing campaigns and give you a better deliverability. These are a few of the reasons why it is so important:

Increase Delivery Rate

Verified email addresses are more likely to be delivered because you can be certain that they are valid.

Why spend time crafting the ideal email only to send it to dozens, hundreds or thousands of bad email addresses?

When you check email addresses, you ensure that your messages are likely to be received.

Avoid Hard Bounces

An undelivered email is more than just a waste of time.

It will also frequently result in a hard bounce. These are error messages sent by the recipient’s email server to let you know that something went wrong.

If you get too many hard bounces from a email server, it may start filtering all your messages to spam.

Maintain Sender Reputation

Email servers aren’t the only ones looking for bad emails.

Service providers are also checking your bounce rate. If they see that you are sending too many emails to bad addresses, they may blacklist you. This can have even further-reaching implications than spam filtering.

You may find more and more of your emails bouncing, even if they are sent to valid addresses.

Check for Catch-All Emails

Some email servers use catch-all addresses, accepting all the emails that aren’t sent to valid email addresses at that domain.

There are two problems with this.

First, a catch-all may send a hard bounce even though the email is received.

Second, chances are good that no one is actively reading the email received by the catch-all.

Get Clearer Email Campaign Metrics

Beyond the damage to your email delivery rate, bad email addresses can also cause misleading email campaign metrics.

You may see an abysmally low open rate and click-through rate, for example.

However, this may simply be because half of your list is made up of unverified emails.

Save Money

When you store and send to email addresses, you are incurring costs of both times and IT resources.

While a handful of bad email addresses won’t have an impact, if you have a major problem, you could be wasting significant money.

Cleaning up your mailing lists is good for your bottom line.

Purge Temporary or Deleted Addresses

An email address does not need to have always been bad to be a problem.

Many people create temporary addresses to sign up for things or delete their older addresses.

In either case, emails that once worked may stop suddenly.

Actively cleaning your list will get rid of these problem addresses.

Find Typos

You may have bad email addresses in your list that are simply typos. For example, [email protected] may be written as [email protected] (the “m” switched for an “n”).

A rigorous email verification process can find these typos. You can then correct them and deliver your email as intended.

With the right toolset, it is easy and time-efficient to check email addresses. With so many benefits, there is little reason not to implement an email verification strategy.

When You Should Check Email Addresses?

You don’t need to verify your email addresses excessively. It is valuable to verify email lists regularly. However, you only need to check if there has been a major change to your list or if you are struggling with poor metrics.

For example, you want to verify email addresses when they are added to your list. You also want to check email validity if your bounce rate exceeds 2% or your open rate is low.

In addition, it is a good idea to clean up your lists on a regular schedule. Consider checking roughly once per month. If you have a relatively small number of emails, you may be able to do this quarterly.

If you have very long lists that change a lot, you may need a more frequent schedule.

Please note that B2B lists need to be validated more often than B2C.

How to verify email addresses?

Email address verification is the process of checking to determine if an email address exists. When you are sending out emails, you want them to go to a real person.

One of the best ways to ensure that they do so is to check email addresses on your list to ensure they are valid. Verification is a valuable tool in any email marketer’s belt. Deciding to validate the email addresses on your list, allows you to eliminate invalid addresses and disposable email addresses which results in improving your sender reputation and keeping your email account healthy.

Sending Email and Managing Bounces

Email validation is a simple way to improve your email campaign and in general your email marketing. The simplest way to verify an email address is to simply send an email to it. If you get a hard bounce, you can remove the email from your mailing list. This is an inelegant solution. It can harm your sender reputation, get you added to spam lists and mess up your metrics. Sending test emails is better than continuing to email bad addresses. However, there are some better options.

Nonetheless, you should check your soft and hard bounces regularly. This is a great chance to clean up your list in between verifications.

Sending Email From Another Email Address

Another approach is to send a test email from a dummy account. This is an extremely simple solution and moderately fast.
All you need to do is sign up a free account then send a test email.

Since it is from an alternative domain name, you can write almost anything in your email body. When you get hard bounce responses, you can remove them from your email list.

The main advantage of this approach is that it is very easy, even for tech novices. However, it is often inaccurate because you may not get clear responses and your messages could be filtered to spam folder.

Additionally, you will need to keep track of the responses yourself using a spreadsheet. For many email marketers, this is overly time-consuming and frustrating. Not to mention the fact that it is just bad to spam your recipients’ inboxes!

How To Verify Email Address without sending an email?

Verification of an email address without sending an actual email is possible, though is a complex process and may require some advanced techniques.

In this section we’ll cover two alternative methods: creating your own solution, and using an Email Verification Service.

Check the email syntax

First step of identifying invalid email addresses is to validate the email address syntax.

Valid email address consist of two parts: a local part (i.e. username) and a domain, separated by a “@” character and follows following format [email protected]

Local part may be maximum 64 characters long and can consist of:

• uppercase and lowercase Latin letters A to Z a to z
• digits  to 9
• special characters !#$%&'*+-/=?^_`{|}~
• dot . , however it should not be at the beginning or the end of local part and it should not be next to another dot

Domain may be maximum

• uppercase and lowercase Latin letters A to Z a to z
• digits  to 9
• hyphen - , however it should not be at the beginning or the end of the domain part
• dot . , used to separate parts of domain labels (subdomains, main domain, and top-level domain)

One could describe those rules in a form of Regular Expression that would look as follows:

[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?

Ping the Server

Next step in the process of email verification is to ping the mail server and ask it whether the address is valid.

This process is slow, cumbersome and very risky for your infrastructure, as you can likely tell. However, it is quite accurate.

You need a tool such as Telnet on Windows or PuTTY or nc (netcat) on MacOs.

Here are the steps needed to verify email address by pinging the email server:

1. Look up the mail server using the command “nslookup -type=mx” followed by the email domain name.
   This should return several servers.
2. Pick one of them and connect to it using Telnet.
   The command for this is on Windows is “telnet {mail server address} 25.”
   The command for this is on MacOs is “nc {mail server address} 25.”
3. Then, say hi to the server by typing “EHLO {your domain name}”.
4. Finally, it is time to check the email address. Start by typing “mail from:<{your email address}>”.
5. Then, after the response code, type ”rcpt to:<{the email you are verifying}>”.

Here’s how the communication would look like for a deliverable email address:

220 mx.google.com ESMTP h3si7768221lfu.32 - gsmtp
EHLO mydomain.com
250 mx.google.com at your service
mail from:<[email protected]>
250 2.1.0 OK h3si7768221lfu.32 - gsmtp
rcpt to:<[email protected]>
250 2.1.5 OK h3si7768221lfu.32 - gsmtp
quit
221 2.0.0 closing connection h3si7768221lfu.32 - gsmtp

And here’s how it would look like for an undeliverable address:

EHLO mydomain.com
250 mx.google.com at your service
mail from:<[email protected]>
250 2.1.0 OK l26si4867318ljg.18 - gsmtp
rcpt to:<[email protected]>
550-5.1.1 The email account that you tried to reach does not exist. Please try
550-5.1.1 double-checking the recipient's email address for typos or
550-5.1.1 unnecessary spaces. Learn more at
550 5.1.1  https://support.google.com/mail/?p=NoSuchUser l26si4867318ljg.18 - gsmtp
quit
221 2.0.0 closing connection l26si4867318ljg.18 - gsmtp

While proceeding with this method, very important aspect is to properly recognise the responses of an email server. Important part of the server SMTP response are so called Basic status codes and Enhanced status codes.

Basic status codes consist of 3 digits, where the first digit represents whether the response is:

• 2 – positive
• 3 – positive intermediate
• 4 – transient negative
• 5 – permanent negative

The second digit represents the category:

• 0 – syntax
• 1 – information
• 2 – connections
• 5 – mail system

Here are some common status codes with their meaning:

• 220 – connected – service ready
• 221 – goodbye – service closing transmission
• 250 – requested action OK and completed
• 450 – requested action not taken – mailbox may be temporarily blocked for policy reasons
• 500 – syntax error – command unrecognised
• 503 – bad sequence of commands
• 530 – authentication required
• 550 – mailbox unavailable
• 551 – user not local
• 552 – exceeded storage