Restrictions on sends in HELO commands
smtpd_helo_restrictions
This parameter specifies optional restrictions on what SMTP clients can send in
SMTP HELO and EHLO commands.
The default is to permit everything. The following restrictions
are available:
- 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_non_fqdn_hostname: reject HELO hostname that is not in FQDN form
- check_helo_access maptype:mapname: look up HELO hostname or parent domains.
Reject if result is REJECT or "[45]xx text".
Permit otherwise.
- check_client_access maptype:mapname: see
smtpd_client_restrictions.
- 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.