Synchronous error: the remote mail server contacted by the Adobe Campaign delivery server returned an error message. Adobe Campaign qualifies each error in order to determine whether or not the email addresses concerned should be quarantined. See Synchronous errors.
Asynchronous error: a bounced mail was resent later by the incoming server. This mail is loaded into a technical mailbox the application uses to label messages with an error. After an email sending failure, Adobe Campaign applies many rules to categorize the error message.
A retry will happen only in case of a synchronous error. More information about it on our official page Quarantine management
If in case the error you are facing is asynchronous, there will be no retry even though it is marked as a soft bounce. It is still marked as Soft so that if there are 5 consecutive errors (obviously over 5 different email) the system marks that address in quarantine.
Please do check if the error captured against your address is a synchronous error or asynchronous.