First, sorry for my english and good night I have two mail server: 1 ISPConfig 3 Server - mydomain.com.br. 1800 IN MX 1 mail.mydomain.com.br. 2 AWS WorkMail - mydomain.com.br. 1800 IN MX 10 inbound-smtp.us-east-1.amazonaws.com. if i send to user created in aws workmail, i receive this message: Requested action not taken: mailbox unavailable 550 5.1.1 <email@example.com>: Recipient address rejected: User unknown in virtual mailbox table How to enable this user to receive mails?