Hello, I've found in this forum a guide about configuring your postfix with multiple domains, but I have a problem. (This was the post: https://www.howtoforge.com/communit...elays-for-different-domains-in-postfix.82711/) My question is, why if I configure my postfix in this way, it works fine. relayhost = smtp.eu.mailgun.org:587 smtp_sasl_auth_enable = yes smtp_sasl_password_maps = static[email protected]assword smtp_sasl_security_options = noanonymous So avoiding the sasl_passwd and doing it directly. In this case, I've no problems; the emails leave the server and are going to be accepted from mailgun. But if configure following the guide: Postfix smtp_sasl_auth_enable = yes smtp_sasl_security_options = noanonymous smtp_sender_dependent_authentication = yes smtp_sasl_password_maps = hash:/etc/postfix/smtp_sasl_passwd sender_dependent_relayhost_maps = hash:/etc/postfix/sender_relay smtp_sasl_passwd @domain [email protected]ass @domain2 [email protected]ass @domain smtp.eu.mailgun.org:587 @domain2 smtp.eu.mailgun.org:587 I got back this error: smtp.eu.mailgun.org[188.8.131.52] said: 550 5.7.1 Relaying denied (in reply to MAIL FROM command)) I've no idea... Thank to who would like to help me!