...
>You might want to use the ACL for HELO or EHLO called 'acl_smtp_helo'.
>
>> Pointer to the relevant parts of the docs will be enough. :-)
>
>ACLs are explained in the specs, chapter #37.
>
>In short: Set an ACL variable in acl_smtp_helo, and refer to it in
>acl_smtp_mail - if it's not set, you may quit the session as there was
>no ehlo/helo.
>
>Could be there are simpler solutions...
Possibly. Just check the value of $sender_helo_name. If it's
null, chances are the connecting client didn't issue an EHLO/HELO
greeeting.