hard bounces versus soft bounces

Soft Bounces - A deferred email is retried for a 72-hour period, but the number of retry attempts varies from receiver to receiver until we get a true soft bounce. Soft bounces are not going through and will not be retried for this particular Campaign but are still eligible for future Campaigns (soft bounces and deliveries are mutually exclusive).

When soft bounces occur, the email address was valid and the email message reached the recipient's mail server but the message was rejected for a "temporary" issue. Common soft bounce reasons include:

• The mailbox was full (the user is over their quota)
• The server was down
• The message was too large for the recipient's inbox

Though they are not tracked in Campaign analytics, dashboard users can monitor soft bounces in the Message Activity Log within the Developer console. These logs also include the reason for the soft bounce. Note that soft bounces can explain discrepancies between "sends" and "deliveries" that may arise within email campaigns.

Although you may expect that soft bounces will eventually turn into hard bounces (as some ESPs do), Braze will not report hard bounces if an email continues only to soft bounce.

Hard Bounces - This applies to email addresses that are invalid or do not exist. When a hard bounce occurs, Braze marks the email address as invalid but does not make any changes to the user's subscription status. We will not make any attempt to send to these email addresses in this state.

Further information can be found on the Braze documentation hub under 'Bounces Invalid Emails'.