Error: 550 5.0.0 - H:DAD or H:MXB Connection Refused due to Abuse

These are new systems designed to reduce the overall amount of spam we receive, as well as reduce the amount of processing power our servers waste on handling spam messages. This error can be received as the result of any attempt, incoming or outgoing, to make a connection with our mail servers from an IP that has been blocked by one of our systems.

H:DAD – Blocking based on servers which seem to be the source of a “dictionary” or brute force style spam attack.  (Sending emails to large list of emails, randomly generated or based on words from the dictionary)

H:MXB – Designed to block servers which we have caught sending us large amounts of spam and little to no legitimate mail.

Information Required for Tickets

  1. For this error, it is absolutely vital for us to examine the bounce-back message
  2. Full header information from the original message.
  3. If nothing else is available, at the very least, we need the domain that is having problems sending.  However, we cannot guarantee that this will be enough information to fully solve the problem.
  4. Obtain the sender’s WAN IP (using a utility such as whatismyip.com)


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