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The mail system
: host us2.mx3.mailhostbox.com[208.91.199.205] said:
550-5.1.1 : Recipient address rejected: User
unknown in virtual alias table 550 5.1.1 Please see
http://support.mailhostbox.com/email-administrators-guide/error-codes for
explanation of the problem. (in reply to RCPT TO command)