I don't think you understand what I am saying; there are sites and software that you use to manage this type of emailing. Sending a mail out to a huge user list using your email client is just a really bad way of doing this. There are various, better ways of doing this and they don't need to cost much. I am happy to help you with this if you would like. I am actually surprised your ISP hasn't flagged this up to be honest (unless you manage your own email servers). Also, mass emails need to be dealt with different or else you simply won't reach the target mail box, sooner or later you will end up on yahoo's naughty list and your email will go straight to junk.
If you think I meant unsolicited email then sorry for the confusion.
If you think I meant unsolicited email then sorry for the confusion.