MX lookup fallback to A

[KSB]

Hi!
I have in config
ignore_mx_lookup_error = no
as default. Which, as I understand, don't force to look for A record, if 
MX not found. But in logs I clearly see, that is tried to deliver mails 
to ip address which corresponds to domain A record if domain haven't MX. 
It is needed for some RFC and can this behavior be changed, to not try A?

--
KSB