[Exim] [Newbie] local delivery not working

Hi folks,
sorry for newbie's question. I set up an exim 4.31 on MacOS X 10.3.3
client. Sending emails works as expected but I'm unable to receive
mails. Watching exim started in command line I found that the mails are
correctly received by it, but stuck inside of /var/spool/exim/input.
Also, executing exim -bp results in list of received mails. Could
anyone point me to the right direction?

My local delivery setup is as follows:

local_delivery:
driver = appendfile
file = /Users/$local_part/mail/INBOX
delivery_date_add
envelope_to_add
return_path_add

The second question is that I have seen some conf soubor having
mbx_format parameter but my exim installation refuses to work with it.

Thanks a lot
Robert