Bounce-Mail Error: 550 5.1.1 xxxxxxxxxx@xxxx.xxx: Recipient address rejected: User unknown

This error can have many causes. All of them boil down to the fact that the recipient to whom this message should be sent is not set up / does not exist on the mail server responsible for the domain.

The following are possible solutions:

1. The most common cause is a typo in the recipient’s email address. Please check this. The entire email address must be 100% correct (both before and after the @ sign). Fix the typo and the delivery will be possible.

2. Maybe the e-mail address to which this message should be sent is actually not set up on the responsible mail server. If the error occurs when sending to one of your addresses at Mailix, simply set up the corresponding e-mail address as a mailbox or alias address and delivery will work.

3. If there was no typo and you are sure that the e-mail address is set up correctly, the last possibility is that the mail server where the address is set up is not yet or no longer responsible for the domain in question. This can happen if the domain has changed it’s servicing provider. The solutions here would be to either transfer the domain back to the existing provider (where the email address is set up) or to set up the email accounts and addresses with the other provider. If one of these has been done, the delivery will work.