Manipulates the list of allowed and disallowed destination domains used by the SMTP proxy.
Usage:
mail_relay add relay_domain
mail_relay add !relay_domain
mail_relay del relay_domain
mail_relay del !relay_domain
mail_relay list
add adds a domain suffix string to be allowed (or disallowed, if preceded by a !) in recipients of mail messages.. del deletes a domain suffix string. list produces a list of the current set of relay domain suffixes.