Postfix Forward Email To Another Email Account

I've multiple virtual domain hosted on CentOS Postfix server. How do I forward selected virtual domain email to yahoo / gmail or other email account using Postfix email server?

Postfix can be configured as mail forwarding domains server using virtual_alias_maps settings. There are two type of configurations here.

Postfix Mail Forwarding Domains

This is useful if you do not have local mailboxes and server is not acting as MX backup (do not use the following if relay_domains sql map or virtual map is configured). The main purpose of these domains is to forward mail elsewhere. The following example shows how to set up cyberciti.com as a mail forwarding domain. Open main.cf file, enter:
# vi /etc/postfix/main.cf
Make sure following two line exists:

 
virtual_alias_domains = cyberciti.com
# virtual_alias_domains = cyberciti.com example.com moredomains.com ..
virtual_alias_maps = hash:/etc/postfix/virtual
 

Open /etc/postfix/virtual file, enter:
# vi /etc/postfix/virtual
Forward email sent to vivek@cyberciti.com to vivek@nixcraft.co.in:

 
vivek@cyberciti.com   vivek@nixcraft.co.in
 

You can also implement a catch-all address i.e. email sent to tom@example.com and jerry@example.com should be forwarded to somewhereelse@another.domain.com

 
@example.com         somewhereelse@another.domain.com
 

Save and close the file. Type the following command to restart postfix:
# postmap /etc/postfix/virtual
# service postfix reload

Postfix Mail Forwarding Domains For Backup MX Server

If your server is a backup mx with relay domain configured via mysql / ldap proxy map only add virtual_alias_maps = hash:/etc/postfix/virtual to main.cf file. Create /etc/postfix/virtual file as described. In other words do not list domain cyberciti.com in BOTH virtual_alias_domains and relay_domains. Use only one configuration option. Usually, relay_domains is configured for backup postfix MX servers.
Please note that you can also use procmail to forward email to another account.