Ben's notes

Reject reason: Helo command rejected: ACCESS DENIED. Your email was rejected because the sending mail server does not identify itself correctly (.local);

• Edit /etc/postfix/helo_access.pcre if needed.
• Restart postfix.

Quote from forum:
It means your client's MTA uses a FQDN hostname which ends with '.local' as HELO identity.

'.local' is not a valid top domain name, and all mail servers should use a valid domain name. You have two solutions:

• Ask your client to change their HELO identity which sent by MTA to a valid one.
• Remove this HELO check rule on YOUR server, in file /etc/postfix/helo_access.pcre.

Personally, i suggest you try #1 first.