Non-ASCII chars in MAIL FROM envelope

[Simon Matter]

Hi,

Running postfix as an MTA I have the problem that postfix accepts mail
with non-ASCII chars in MAIL FROM envelope and cyrus-imapd's lmtpd rejects
them with "501 5.5.4 Syntax error in parameters".
>From what I understand 8bit envelopes are allowed according to newer RFC's
and I'm wondering if it's correct that cyrus-imapd blocks them if they are
found in MAIL FROM, not RCPT TO?

I know it's possible to use check_sender_access in postfix to stop those
mails from being accepted, but it seems it could still block legitimate
mails despite that fact that those from adresses may be 99.9% spam.

How do others deal with this issue?

Thanks,
Simon