My Spam filter seems to be blocking people that have been able to email us for years. This all started on Friday the 21st of June and is continuing to get worse. I have added them to the safe senders list, dropped the sender reputation down to 0 and have checked the subject and there are no keywords listed that would mark it as Spam. Any ideas or is anyone else having this problem.
Oh and the server is up to date with Windows Updates.
I am using Windows SBS 2011