Four types of bad destinations you should exclude from all traffic

Sending traffic to non-existent or invalid destinations can hurt your performance and even damage your IP reputation. With MailerQ's Suppression List you can preemptively prevent unnecessary connections to bad destinations that have shown to be harmful for different reasons. In this blog post we'll discuss four different types of 'bad' destinations and explain how including these on your Suppression List can be beneficial to your email operations.

1. Non-existing domain name

Before attempting to deliver a message, your Mail Transfer Agent (MTA) queries the MX records for the receiving domain in order to specify the receiving mail server. If no MX records can be found for a domain this results in a failure which means your mail will briefly be exempted from delivery. This kind of failure can either be caused by a temporary downtime of a DNS server or due to a typo in the domain name. In either case, your MTA automatically reschedules the mails for later delivery at increasing intervals.

Now, when the failure is caused by a temporary downtime of a DNS server, the delivery re-attempts are relatively harmless. After all, there is a high chance that your mail will eventually be delivered without interference necessary. However, when the failure is caused by a typo in the domain name, the delivery attempts are a waste of your MTA's resources and traffic which can eventually hurt your overall performance. Since no MX record can be found for these domains, your mail can not be delivered regardless of how many delivery re-attempts are scheduled.

In order to prevent this, you can include common typos in domain names on your Suppression List in MailerQ. Think of domain typos like 'gmai.com' or 'hotmal.com'. Upon a delivery attempt, the recipient's domains are then first matched with the Suppression List and upon a match are excluded from delivery for every matching message. This makes MailerQ discard the suppressed messages before any delivery attempt is made, so that it doesn't have to waste unnecessary resources on lookups and delivery attempts.

2. Non-existing mailbox

Sending traffic to invalid domain names can primarily hurt your performance, but sending traffic to invalid usernames on a domain can hurt your performance and your IP reputation. If you send a lot of emails to non-existent usernames on a domain it will result in a lot of hard bounces. This not only means that the load on your MTA will be increased with backscatter bounce messages, but also increases the likelihood that ISPs will mark you as a spammer or bad sender.

If you include non-existent recipient addresses on your Suppression List, you can stop delivery attempts to these destinations for all customers. This also saves resources spent on manual bounce processing.

3. Non-human mailboxes

Sometimes bot registrations end up on your sending list. Sending emails to these bots can distort your clients' email metrics and hurt your IP reputation. For instance, imagine if you send a lot of emails to non-human mailboxes and none of them are opened and clicked. This tells a message to Internet Service Providers (ISPs) that a lot of people are not interested in your emails, which means that there is an increased risk that your messages will be marked as spam.

In other cases bot registrations do generate opens and clicks. At first sight, it might seem beneficial for your deliverability to keep these bot registrations on your list. However, sometimes these bot registrations are generated by Mailbox providers themselves to protect their users from bad senders When they discover you're sending to these addresses, it can impact your sender reputation as well. Prevent both of these situations by including known non-human mailboxes on your Suppression List.

4. Bad destinations list

There are many lists readily available with dozens of email addresses that have been proven to be harmful for various reasons, including the three mentioned above. These lists include known bot addresses, bought email addresses, invalid addresses etc. Adding these addresses to your Suppression List prevents you from attempting deliveries to these bad destinations and helps protect your sender reputation.

Wrap up

In the perfect world your clients are doing all they should to prevent these bad addresses from ending up on their list in the first place. Deploying best practices such as using a double opt-in and ReCaptcha forms, and avoiding buying email addresses from third parties can help with that. However, in reality you'll find that many clients don't understand or adhere to the best practices that are necessary to maintain a good reputation and a clean list. Consequently, sending to bad email addresses that end up on the list does not only hurt their own reputation, but also potentially hurts the reputation of other clients that share the same IP addresses. With MailerQ's Suppression List, you can stop delivery attempts to these four types of bad destinations for all clients. Doing so can effectively and efficiently help protect your sender reputation and those of your individual clients.

Eager to try out MailerQ's Suppression List for yourself? Request a free trial!