I have just learned that some of the addresses a client has provided to us were most likely obtained through an append service. Luckily, there's another data point that I can use to distinguish between ones that were probably obtained with explicit consent to be marketed to, and the ones that may or may not be, and I haven't mailed the gray area addresses yet. I realize that it's bad practice, but I also want to know if I am going to end up violating Acceptable Use Policies / Terms of Service, and/or laws if it comes up. Is there a consenus about this? Are there some circumstances where email obtained through an append service are considered non-spam?