If you put multiple addresses in a .forward file, a copy will be sent to each.
remoteuser1@domain.tld, remoteuser2@domain.tld, remoteuser3@domain.tld If you want to keep a copy of each message in the original account without causing a .forward infinite loop, put a backslash in front of the account name.
\localuser, remoteuser1@domain.tld, remoteuser2@domain.tld, remoteuser3@domain.tld 