This method can only be applied to mailings of type DOI
Returns the DOI key of the mailing with the provided id.


Parameter Default Description
mailingId Optional parameter. If filled, the unsubscription event will be counted for the mailing with the given ID and will be visible in the reports. Note, that you will get an error '400 – Bad Request', if you specify a mailing that has not been sent yet (i.e. has not the state 'sealed' and is still a draft).