I regularly get a few calls a month about this issue, so I decided to (finally) write a post about it. If your anti-spam software or appliance is set to block ad links to doubleclick.net (as mine is), you’ve undoubtedly faced this issue as well. Some, but not all messages from aol.com mail users will be blocked. This is caused by AOL’s automatic message footer which includes ads from various online ad services, doubleclick.net being the most prevalent. This reminds me that I need to tune the filter to block the other ad agencies footer content as well.
All is not lost, there is a way for the average AOL mail user to disable the problematic message footer. Thanks to Microsoft MVP Bill Pytlovany who has provided clear and concise instructions on how to disable the message footer, which I have reproduced below based on his original post:
AOL users can click the following, remove the check box next to Show the message footer at the bottom of each email you send. and click Save.