[exim] How to discard emails with empty from field

Hi,

i have an important quantity of emails in exim queue that when I do
exiqgrep -b it show, something that:

1VJmd0-0006lJ-CD From: <> To: yyyy@???

Take note of From field = <> !

I think that those emails are all SPAM.

My questions:

1) Is rigth that when from field is equal to "<>" the email is a SPAM?

2) Can I set something on exim configure to discard those emails
automatically without relaying it? What? How?

Can anyone help me?

Thanks in advance.

Jorge Colaccini