Leads are given the Blacklisted status for 3 general reasons:
Permanent failure code – The lead’s email address is invalid. This could be because the email address does not exist, is in the incorrect format, the domain tied to the email address is invalid, and so on.
Suppressed failure code – The lead has indicated that they do not want to receive emails from the Mailingboss system. This is usually caused by a lead unsubscribing from the mailing list or sending a complaint response, such as marking the email as spam or blocking the sender.
Temporary failure code – The lead’s email address is temporarily unavailable. This is most often due to the recipient’s mailbox being full or inactive/disabled. The email address is removed from the mail queue and after 24 hours, Mailingboss system will attempt to send the email again. If the delivery was successful, the lead will be taken out of the Blacklisted status. If not, the Mailingboss system system will keep trying to send the email every 24 hours unless the email returns a Permanent/Suppressed failure code, where the lead will remain in the Blacklisted status.