There are two types of bounces which are handled differently as explained below: 

Soft Bounce: This is a temporary issue such as the recipients inbox is full, the email message is too large, or a connection timeout. 

We will automatically attempt to resend the email. If it cannot be delivered after a certain number of attempts, the recipient will be “Blocked” for 90 days. After the 90 days, the email address will be active again.

Hard Bounce: This is a permanent delivery error which can be caused by the following: 


  • An invalid email address (e.g. a mis-typed email, the email no longer exists -  i.e. the person has left the company or a non-existent destination server - it is not a valid email or domain name). 
  • Emails can also hard bounce if the recipients email server rejects the email and so it is blocked from being sent to the recipient. 
  • This may happen if the recipients email server runs spam checks and also DNS checks, for instance if SPF or DKIM records are not set up then the email can be rejected by the email sever - even if it is a valid email address. 
  • The recipients email server may also look at the IP addresses of the email server that the email is coming from - if the IP address is found on a blacklists then this can be why the recipients email server rejects the email and so it is blocked.


Hard bounces negatively impact your sender reputations and are automatically blocked.  

What is an acceptable bounce rate?


8% or below is an acceptable bounce rate any higher than this would indicate that your data is old with email addresses no longer being current.