I'd like to accept mail for a domain not currently hosted on my server (CentOS, SMB Plesk, provided by 1&1).

I'm scared of editing /etc/postfix/main.cf virtual hosts entry, for fear of messing with the Plesk setup. This is what it currently reads:

virtual_mailbox_domains = $virtual_mailbox_maps, hash:/var/spool/postfix/plesk/virtual_domains
virtual_alias_maps = $virtual_maps, hash:/var/spool/postfix/plesk/virtual
virtual_mailbox_maps = hash:/var/spool/postfix/plesk/vmailbox
virtual_mailbox_base = /var/qmail/mailnames
virtual_uid_maps = static:110
virtual_gid_maps = static:31
virtual_transport = plesk_virtual
plesk_virtual_destination_recipient_limit = 1

When I look at the specified locations, all I find are *.db files ...

Please help.