It is up to the 3rd party email server to honour the bounce mail header. This is a standard header, so if the 3rd party email server does not read this header and does not return bounced mail, DB Mail will not be able to pick it up.
It is up to the 3rd party email server to honour the bounce mail header. This is a standard header, so if the 3rd party email server does not read this header and does not return bounced mail, DB Mail will not be able to pick it up.