Dear friends, I have a VPS with multiple domains hosted. Over time I was a problem with shipping to accounts 'hotmail.com'. The solution I found was to hire an SMTP service to relay e. I had to configure Postfix to have some authentication data for each domain. Here attached configuration for which you can serve: /etc/postfix/main.cf smtp_sasl_auth_enable = yes smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwords smtp_sasl_security_options = noanonymous smtp_tls_security_level = may start_tls = yes header_size_limit = 4096000 smtp_sender_dependent_authentication = yes sender_dependent_relayhost_maps = hash:/etc/postfix/sender_relay relayhost = /etc/postfix/sender_relay @dominio.com [smtp.servidorsmtp.com]:25 /etc/postfix/sasl_passwords #[smtp.servidorsmtp.com]:25 usuario:clave @dominio.com usuario:clave postmap /etc/postfix/sender_relay postmap hash:/etc/postfix/sasl_passwords /etc/init.d/postfix restart This configuration works well for the relay of all emails in each domain. My question now is whether there is a Postfix configuration allowing the relay emails sent only to 'hotmail.com' for each domain. That would solve my problem, because the only emails I am having reception problems are with 'hotmail.com', others are working properly and I can send to my VPS server. Thank you very much in advance.