Well I dont use my ISP for email normally, I do have an email account with them but dont really use it. My mail emails are handled by my hosting company which works very well and has good spam control. I do get emails returned as undeliverable on occasions and usually for very good reasons but it is very few. I am not aware of any of mine going into a black hole, just a few times when my hosting company server gets on a black list some come back but it gets sorted very quickly.
Stuart