[Exim] acl to block sender

On a typical log line like so:

2003-09-19 05:49:02 H=(mailin-04.mx.aol.com) [68.115.146.58] F=<joe@???>

what would you use in an ACL to deny on the "mailin-04.mx.aol.com" ?

It is my understanding that senders would be the F= line
what is the H= line ??

--
Jim Pazarena  Box 550                 mailto:paz@qcislands.net
              Queen Charlotte  BC     http://www.qcislands.net/paz
              CANADA   V0T 1S0        phone:250 559 7777