I think we've all heard cautionary tales about how careful spam filter monitoring is important to authors, with all the submissions and correspondence that we do through email, but I received another reminder Wednesday.
I always check my spam email box, and I'm glad I did, because my acceptance from Daily Science Fiction landed there.
This doesn't happen very often, but back in 2004 I had the same thing happen when Andromeda Spaceways accepted "The Cast Iron Dybbuk". The acceptance sailed all the way through the ether from Australia to drop smack dab in my spam.
I think I have pretty good spam filter settings, but in both cases, the acceptances came from an email address that I had never received an email from before, and I had never sent an email to before. That makes sense - you send submissions to one email address, and you get rejects from the slush pile reader. The acceptance come from a different direction.
I suppose the spam filter regards an email address where there has hasn't been any communication before - either coming or going - as suspect.
This certainly highlights the fact you should NEVER set your email to delete spam unread!