When sending a campaign, it may happen and it is quite normal that an email cannot be delivered to certain subscribers, which is what is commonly known as a bounce. These bounces occur for many different reasons and they may be temporary or sometimes permanent.

Bounce rate in a campaign

It is very important to pay special attention to this metric as it gives you information about the quality of your mailing list.

As a rule of thumb, we consider a bounce rate of less than 3% a sign of a healthy mailing list. Usually, subscribers on a quality contact list are obtained by using a double opt-in subscription mechanism which requires confirmation upon subscription.

The bounce rate is calculated by dividing the total number of recipients in your campaign by the number of bounce notifications.

Temporary bounces

This kind of bounce means that the recipient's mailbox was unavailable when your message was sent. Causes of temporary bounces vary. For example, a full mailbox or anti-spam software may cause a bounce. We will attempt to deliver them over a 12 hours period following the initial campaign or until a permanent bounce message is received.

If after the 12-hour period, delivery still remains impossible, we will stop any further delivery attempts to that recipient. Contact will not be removed from your mailing list unless we receive a permanent bounce notification.

Permanent bounce

A permanent bounce usually indicates that an email address is invalid, that an account is no longer active or has been de-activated. You may notice a higher permanent bounce rate when sending to a contact list for the first time. However, if campaigns are sent on a regular basis, you should expect a very low permanent bounce rate.

IMPORTANT: Once an email address is reported as a permanent bounce, we automatically remove it from your contact lists. In other words, the status of a permanently bounced subscriber is considered as invalid. Your future campaigns will no longer be sent to that subscriber. 

In case of error, an invalid subscriber status can be updated to valid again. But, we suggest you proceed with caution as repeated mailings to a subscriber that repeatedly bounces can affect your delivery rate.