Followed you command and getting the following
server:~ admin$ sudo postconf -e "smtpdhelorestrictions = permitsaslauthenticated permit_mynetworks rejectinvalid_helohostname rejectnon_fqdn_helohostname"
server:~ admin$ sudo postfix reload
/usr/sbin/postconf: warning: /etc/postfix/main.cf: unused parameter: smtpdhelorestrictions=permitsaslauthenticated permit_mynetworks rejectinvalid_helohostname rejectnon_fqdn_helohostname
postfix/postfix-script: refreshing the Postfix mail system
The forum software formatting implementation has corrupted various older postings, particularly when there are embedded underscores in the older postings. And embedded underscores are common with Postfix syntax.
I can't tell what you're entering there (reliably) and you haven't stated what problem(s) you're trying to solve, and what I do see posted is incorrect syntax. Your entered command was missing some of the necessary underscores, and didn't do what you wanted, and triggered that diagnostic to try to tell you about the error.
There's a somewhat-similar newer posting in this thread that looks to have correct formatting.
Also check the Postfix documentation, as it's pretty good, and it's quite detailed, there are good overviews of common operations, and it doesn't have the underscore-formatting glitch. In particular, see here and here for general syntax details and for specific spam-related settings akin to the HELO restrictions.
ps: In general, please start your own thread with your question and your OS X Server version, and refer back here with a link. You can't manage a thread you don't start, and we can also see if the forum formatting software also processes the underscores correctly in a new posting, too. AFAIK, it should. It was just the ported / converted / imported postings that got underscore-stomped.