Some mail providers have opted to use spam detection and spam-fighting services. These services often determine what is spam by receiving reports from their users.
If enough people report our mail as spam, then we get listed as being a spammer for a period of time. Depending on the number of spam reports they get, they will block us longer for each occurrence.
Wharton Computing is taking a number of steps to minimize the chance that we get blocked, but it still occasionally occurs. If you have further questions, please submit a ticket or email the Support Team at firstname.lastname@example.org