Postfix doesn't reject empty senders

[Tomàs Núñez Lirola <tomas@grupoeon.net>]

Hi
My smtp server (postfix) was receiving a lot of mails with empty senders  
("mail from:<>"), and it sends them as they was from 
"MAILER-DAEMON@mydomain". I want to change this behaviour, so I added to 
main.cf the line 

'smtpd_sender_restrictions = reject_non_fqdn_sender'

thinking that "<>" is not a fqdn. But after that, postfix still sends them. So 
I added

'smtpd_sender_restrictions = reject_non_fqdn_sender, 
reject_unknown_sender_domain'

but this way I get the same response:

helo k
250 mydomain.com
mail from:<>
250 Ok
rcpt to:some@address.com
250 Ok
data
354 End data with <CR><LF>.<CR><LF>
fds
fdsfsf
fdsfs
.
250 Ok: queued as B4F7C3EFF
quit
221 Bye


RTFM'ing, I don't find any more option to reject this kind of senders, so I 
don't know what to do...
Am I doing anything wrong? Can anyone please help me?

Thank you very much