spamming with friends

One of Mrs McMuffin's oldest friends moved to live in Australia with her husband a few years ago. We last saw them at our wedding nearly three years ago but we get the occasional telephone call and email from them. We also get spam from them too. Mrs McMuffin's friend has tried to set up a variety of businesses over the years, usually trying to sell stuff over the internet. She usually starts these enterprises off by trying to sell to her friends. So, we regularly receive spam from her. My dilemma has always been, and I imagine she is fully aware of this, how do I tell her to F**K OFF without offending her and causing some kind of rift in what is an otherwise okay relationship. I can't just block the email address because this is their usual contact address and we want to stay in touch with them. This morning I'd had enough, and I wrote to her asking her to stop sending us promotional stuff and to take us off her mailing lists. I don't know if anyone else has called her on this, so it will be interesting to see what response I get.