Davide Marchi: > If I shut down the primary server, the MX backup receive the mail > correctly and mail goes into mailbox 'INBOX'.
Well that is the mistake. This server should not deliver to mailbox. Have a look at Postfix documentation: "Configuring Postfix as primary or backup MX host for a remote site" http://www.postfix.org/STANDARD_CONFIGURATION_README.html#backup Wietse
