As simple as it sounds, keeping your contact lists updated is one of the most important factors contributing to email deliverability. Invalid or non-existing email addresses not only stop your email from being delivered entirely to some recipients, but also have a negative impact on the IP reputation and future campaigns, especially if it’s happening on a regular basis. This can be prevented by a thorough check of your logs after every single campaign sent, especially if it was sent to recently added contacts. React accordingly to bounces/errors and make adjustments if necessary.

If you experience issues with deliverability, you can check logs for potential issues. Email bounce means an email has returned to the sender and cannot be delivered to the mailbox. It may be caused by different factors, including invalid email addresses/outdated contact lists. Full article about all email bounces you can find here.

The first step is to check your logs. There are two ways to access this section, depending on the current plan.

FOR “EMAIL API”

Go to “Logs” > “Email log”:

For “EMAIL MARKETING”

Go to the “Audience” section:

Click on “View email logs”:

Click on the “Event” tab to expand the filters list and pick “Bounces” to only see bounce/error-related events (screenshot below):

We’re looking for an event called “Bounced”. In this case, the bounce type is always “Hard” with the description “No mailbox” (example below):

Find all invalid/non-existing contacts and delete them from your contact list.

Event “Bounced” means that an email returned to the sender and cannot be delivered to the mailbox for some reason. Bounce type “Hard” refers to an undeliverable email, so a proper action needs to be taken and such contact - removed or modified.

“No mailbox” means that the mailbox has been deleted, does not exist or the email address itself is invalid (check for typos).

3. Conclusion.

We highly recommend checking your contact lists on a regular basis (weekly or monthly) and Email log after every campaign if it was sent to the recently added contacts/contact list.

It sounds like a minor factor contributing to the email deliverability as a whole, but this relatively minor action not only will prevent this issue from happening in the future but also improves your IP reputation (reduced risk of being blacklisted/blocked/throttled) and it will be beneficial for all future campaigns you send.