Virtual aliases can map to addresses that do not terminate on the local system while regular aliases can only map to addresses which terminate on the local system. Virtual Alias Domains You will need to add these lines to the main.cf file. virtual_alias_domains = example.com If you were going to add a number of domains you would want to create a map file.  Create the file /etc/postfix/virtual_alias_domains and enter one domain on each line ...

Aliases It is important for Postfix to be able to use the alias file on the server (/etc/aliases). To ensure that it is in a format that Postfx can use run the newaliases command. newaliases or run this command postalias The alias file is created in a database that can be used both by Sendmail and Postfix. This has been done so that if you migrate from a Sendmail installation you will be able to move easily to Postfix and use the same aliases. ...