Understanding bounces and suppressions

Learn about hard bounces, soft bounces, automatic suppression, and the reasons why an email might not get to your contacts.


Sometimes your emails won't get through to your contacts' inboxes. When emails fail in this way, they're known as bounces. When this happens, we'll let you know why something has bounced. To access this information in your account, go to Reporting > Campaign reports. After clicking on the campaign you wish to investigate, you will see bounce-specific information in the chart under the 'Delivery report' heading.

Hard bounce vs soft bounce

A hard bounce is an email sent to contacts whose addresses are permanently unreachable, most likely because they, or the server they were hosted on, don't exist. The email address is invalid. A hard bounce will immediately result in the email address being placed in the suppression list.

A soft bounce is an email sent to contacts whose addresses are temporarily unreachable, possibly because their mailboxes are full or their mail servers are having temporary issues accepting email. It doesn't necessarily mean the email address is invalid.

To learn more about the different types of bounces, check out the article Understanding your sender reputation.


If an email address hard bounces once, or soft bounces too many times, it will be suppressed in your account to prevent you from sending to it. This helps to protect your sending address and server from being blocked for spamming.

The platform allows you to set how many times a contact can consecutively soft bounce before they become suppressed in your account.

Soft bounce count resets

The soft bounce count for a contact gets reset to zero if:

  • The contact opens an email campaign sent from your account. 
  • The contact subscribes to your account again.
  • The contact becomes automatically unsuppressed (see below).

Automatic unsuppressions

If a contact on the Global Suppression List (GSL) engages with any email campaign:

  • We remove the contact from the GSL if they were added because they hard bounced, soft bounced, or had no MX record. 
  • The contact’s global soft bounce count resets to zero.

Additionally, contacts are removed from your suppression list after a year if they were suppressed because they reached your soft bounce threshold.

When contacts are unsuppressed for any of these reasons, they aren't automatically added to your account - but they can be created or uploaded again.

Bounce and suppression types

At various points in the system you may see references to bounce types. These are explained below.

  • Globally suppressed: Contacts who've either complained directly to us in the past or are known spam traps.
  • Hard bouncers: Contacts whose addresses are permanently unreachable, most likely because they, or the server they were hosted on, don't exist.
  • Soft bouncers: Contacts whose addresses are temporary unavailable, possibly because their mailboxes are full or their server is having temporary issues accepting mail.
  • ISP complainers: Contacts who've submitted spam complaints to us via their internet service provider.
  • Mail blockers: Contacts who've received messages that their provider does not want to process, possibly because of attachments.
  • Domain suppression: Contacts whose email domain you have previously added to your suppression list.
  • Soft bounce: The mail server that handles mail for this email address didn't accept the message when we tried to send it; however, trying again later may succeed.
  • Soft bounce - DNS failure: Although we tried several times, we were unable to determine which mail server is configured to accept mail for this email address. This may be due to the correct mail server undergoing maintenance at the times we attempted to send the message.
  • Soft bounce - mailbox full: The recipient's mailbox is too full to accept the message you tried to send them.
  • Soft bounce - message too large: The recipient's mail server won't accept a message of this size.
  • Bounce - no email address: A bounce came back, but the mail server we sent the message to didn't indicate who the bounce was on behalf of. We've identified the intended recipient, based on the content of the message being returned.
  • General bounce: The mail server returned the message to us, but didn't indicate a reason why.
  • Mail blocked: The mail server indicated that it didn’t want to receive the mail. No reason was given.
  • Mail blocked – known spammer: The mail server has decided that your message doesn’t satisfy their filtering criteria, and thinks it may be spam. It has been rejected.
  • Mail blocked – relay denied: The mail server says that although the recipient’s domain is pointed at it, it won’t currently accept mail for that domain.
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