Help! Our email server is being inundated with what appears to be similar to guessed at addresses but they are not acutally even close. The "guesses" are junk like "xrrlsjeiso99wq@realdomain.com". This only causes our system to further bog down with sending out a notice to that bogus address it is sent from saying "user unknown". This looks more like a vicious DOS attack than spammers trying to find addresses or send spam. We've also found that some apparent virus is causing spam to be sent from our own users machines. Can anyone shed some light on what we can do. AV doesn't seem to catch it anywhere and there is no way to block them. We have addresses sending from our server like brilliantmarketing101@bmmangers.com and @bmupgrade.com and @bmfighters.com. I know they are bogus, but dont' know how to find the server they are coming from.