In case any of you are dealing with SPF on your Exchange system, here are a few tips.
First, ensure that you are modifying the correct external DNS. I recently was attempting to configure an SPF record for a customer, and we were modifying what we thought was her external DNS, but it wasn't (anymore). Use nslookup or dig (from a Unix machine) from outside the network to verify that you are modifying the correct DNS.
Second, we found a simple SPF record that works. Here it is:
v=spf1 IP4:type.your.ip.address ~all
Of course, you'll have to put in the IP address of the machine your email originates from, but this seems to be the simplest SPF record you can use.
Third, note that your ISP will probably have to enable reverse DNS for you as well.
If you follow these tips, or have some to share, drop me a line. My info is on the Contact page. Thanks!
