anti-UCE efficacy of smtpd_helo_required

[/dev/rob0 <rob0@xxxxxxxxx>]

This may be borderline in topicality, but I just got handed (by 
surprise) a rather busy domain to host, and I would like to know from 
those who use it, how effective have you found "smtpd_helo_required" in 
curtailing spam? Are there known brain-dead SMTP MUA's which don't say 
HELO? I just don't want to risk losing real mail.

I tried to test this myself using
[main.cf]
    smtpd_helo_restrictions =
        warn_if_reject check_helo_access regexp:/etc/postfix/helo
[/etc/postfix/helo]
    !/./                   452 A proper HELO/EHLO, please
but that seems to match everything, HELO or no HELO. I'm telnet'ing to 
the smtpd, not saying HELO, and sending mail with no reject_warning.

I thought about it a bit and figured that smtpd_helo_restrictions might 
not be applied to a null HELO. So I took that out and added it here:
[main.cf]
smtpd_recipient_restrictions =
     warn_if_reject check_helo_access regexp:/etc/postfix/helo,
     permit_mynetworks, reject_unauth_destination
I telnet'ed in from outside $mynetworks, no HELO, still no warning.

How do I match a null HELO/EHLO other than with smtpd_helo_required? Or 
should I stop worrying and learn to love the smtpd_helo_required?
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