Restrictions on recipient addresses
smtpd_recipient_restrictions
This parameter specifies restrictions on recipient addresses that SMTP clients
can send in RCPT TO commands.
These destinations do not need to be listed in
$relay_domains.
The following restrictions are available (* is part of default setting):
-  *permit_mynetworks: permit if the client address matches
        $mynetworks.
-   reject_unknown_client: reject the request if the client hostname is unknown.
-   reject_maps_rbl: reject if the client is listed under
        $maps_rbl_domains.
-   reject_invalid_hostname: reject HELO hostname with bad syntax.
-   reject_unknown_hostname: reject HELO hostname without DNS A or MX record.
-   reject_unknown_sender_domain: reject sender domain without A or MX record.
-  *check_relay_domains: permit only mail:
	Reject anything else.
-  permit_auth_destination: permit mail:
-  reject_unauth_destination: reject mail unless it is sent
-   reject_unauth_pipelining: reject mail from improperly pipelining spamware
-   permit_mx_backup: accept mail for sites that list me as MX host.
-   reject_unknown_recipient_domain: reject domains without A or MX record.
-   check_recipient_access maptype:mapname: look up recipient address, parent domain, or localpart@.
	Reject if result is REJECT or "[45]xx text".
	Permit otherwise.
-   check_client_access maptype:mapname: see
        smtpd_client_restrictions.
-   check_helo_access maptype:mapname: see
        smtpd_helo_restrictions.
-   check_sender_access maptype:mapname: see
        smtpd_sender_restrictions.
-   reject_non_fqdn_hostname: reject HELO hostname that is not in FQDN form.
-   reject_non_fqdn_sender: reject sender address that is not in FQDN form.
-   reject_non_fqdn_recipient: reject recipient address that is not in FQDN form.
-   reject: reject the request. Place this at the end of a restriction.
-   permit: permit the request. Place this at the end of a restriction.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
NOTE: YOU MUST SPECIFY AT LEAST ONE OF THE FOLLOWING RESTRICTIONS
OTHERWISE POSTFIX REFUSES TO RECEIVE MAIL:
	reject, check_relay_domains, reject_unauth_destination