Why we insist on email address verification for our clients

Oct 12, 2020 | Best practice, Email marketing

People change jobs, companies close, and over time the email addresses on your mailing list become invalid.

Melaina Gross


We all want to maximise the number of our emails that get read, as well as save money on mass emailing. Since mass emailing services often charge by the number of recipients on the mailing list, removing inactive accounts and avoiding the spam box helps businesses get the most bang for their buck.

What happens to email addresses on my list that aren’t valid?

When your mailing list contains email addresses that no longer exist and you try to send them your newsletter, the email bounces back. This shows up as a hard bounce in your campaign report.

Email sending platforms will automatically not send future emails to the email addresses that have bounced. If you’re sending mail to your list from the platform fairly regularly, you should be okay. But if you haven’t mailed the people on your list for a while (more than 3 months), or you’re mailing them for the first time, you’ll benefit from verifying their email addresses first.

What happens if I send mail to email addresses that don’t exist?

Understandably, you might think that a great way to clean out your invalid addresses is to send your newsletter and wait for the report. But each email sending platform has its own policies and levels of tolerance when it comes to invalid email addresses.

The impact of a high bounce rate

When emails can’t be delivered, a status of hard or soft bounce is given to the address. It’s important to guard against a high bounce rate. A hard bounce is marked as invalid immediately, while a soft bounce occurs when there could be a temporary issue with a mailbox (for example, the mailbox is full). Typically, a soft bounce will automatically convert to a hard bounce after a soft bounce has been returned in three consecutive campaigns.

Some platforms are very strict! If your campaign has a bounce rate of more than 2%, your account could be suspended. It’s hugely inconvenient if you can’t gain access or export your lists until you’ve cleared the issue with the platform’s support team. Sometimes it’s not possible to fix the problem at all, and you’re forced to start from scratch on an alternative platform.

The impact of hitting a spam trap

Another problem with sending emails to old addresses is that some of these could be used to create recycled spam traps. Anti-spam organisations, Internet Service Providers (ISPs), and corporations use old email addresses and reassign them to spam trapping in order to identify spammers sending email to their domains. If you send to a spam trap, your sending domain and IP addresses will be blacklisted, and it will impact your sender reputation. This will result in your emails being blocked from delivery. If you’re blacklisted by some of the major anti-spam organisations, it can take a long time to get delisted and your email marketing will basically come to a complete standstill.

This leads us to the value of email address verification…

How email address verification works

Email verification is more complex than simple email validation. An email verification service charges more than an email address validation service.

Email verification tools help to ensure that emails are deliverable. The goal is to reduce bounces, and improve email marketing and outreach campaign performance. Additionally, email verification tools help clean bots and inactive users from your mailing list to ensure business emails hit real, active recipients and avoid the spam box.

There are services available online to perform email address verification. Some offer a free check of a small number of email addresses, while charging more to check bigger lists. They also tend to differ in the levels of checking they do. And some are better than others! We prefer to have a handle on every step of the process and have teamed up with an expert partner, Blazon, to offer this service to our clients.

We offer a stringent service with thorough levels of checking:

  • Syntactical
  • Domain
  • A Record
  • MX Record
  • Reverse DNS
  • SMTP Server Conversation
  • and we support grey listing retries

For the most part, a list that’s been run through our validation services will be +-98% clean. Unfortunately we can’t guarantee 98% as there are many misconfigured mail servers on the internet.

Grey listing retries

To make sure we get optimum results for our clients, we offer grey listing retries: When a sending SMTP server is communicating  with a receiving SMTP server and the receiving SMTP server is not familiar with the sending SMTP server, the email might soft bounce – asking the sending SMTP server to try again in a certain number of minutes/hours. Because of this extra round of checking, we can arrive at a more accurate, clean list for our clients.

Some verification services don’t include grey listing retries and those email addresses could be inadvertently removed. No one wants to lose valid email addresses!

How long does it take?

Lead times depend on the number of emails and on the responses from the receiving SMTP servers, but it usually takes 24 hours. To be safe, 48 hours. Verifying a million email addresses would probably take a week.

Interested in finding out more about this service?

Fees depend on the number of addresses to be verified. 


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