In Mac OS X Server v10.6, Postfix is configured to require a fully qualified hostname from SMTP clients. This setting is configurable and the restriction can be removed however any modification of a security-related setting should be evaluated prior to making the change.

Once you have evaluated the change you can use the following steps to implement it:

Note: Before proceeding back up the /etc/postfix/ file as a precaution.

Option 1

  1. In /etc/postfix/ locate the smtp_client_restrictions setting
  2. Remove “reject_non_fqdn_hostname” from the list of settings.
  3. Restart the Mail service.

Option 2

  1. Carefully edit /etc/postfix/ (using terminal or a proper text editor) and change:
    • smtpd_helo_restrictions = reject_invalid_helo_hostname reject_non_fqdn_helo_hostname
    • to
    • smtpd_helo_restrictions = permit_sasl_authenticated permit_mynetworks reject_invalid_helo_hostname reject_non_fqdn_helo_hostname