Hello. I'm running PostFix on my server in null-client configuration. So postfix is used to send email only. I receive email via external email provider (Yandex mail for domains). I set my domains MX records to point to provider ones. The problem is that my machine has several domains running on it (with php in fast-cgi configuration). And when PostFix sends email in SMTP session it says something like: Where username is the name of the system user, that invoked sendmail, and hostname is the hostname of the server. Body of email message contains a valid email address in headers. The problem is that many email servers reject emails on MAIL FROM command with invalid email address specified. How do I correctly set PostFix mapping so that each Linux user had a corresponding email address to be used in SMTP communication? I've tried to setup mapping in the /etc/aliases file and putting them to alias_map directive of main.cf, but somehow it doesn't work.