Email blocking
A word of advice to writers who submit stories (to anyone) via email:
If your mail system or ISP blocks mail from people who aren't on your list of specified valid senders, you need to add the magazine editor's email address to your list before you submit the story.
If an editor sends you a rejection note and gets back a bounce message saying "I'm not accepting mail from people I don't know, so if you want this to get through to me, you'll have to visit this URL and submit a form saying who you are," chances are good that the editor will shrug and discard the bounce message, and you will never hear back about your story.
A few months later, you might send a query to ask what happened to your story. If the editor is particularly organized, they might remember what happened well enough to tell you in a response to your query—but then, if you still haven't put them on your accept list, they'll get the same bounce message they got before. You may never find out what the editor thought of your story, and you may waste months waiting for answers that will never come.
The latter half of the above scenario (author queries, response to query gets bounced) hasn't quite happened with us yet, but similar things have.
Really, this is just part of a more general point: if you're going to engage in business correspondence via email, and you have a filter on your incoming mail that blocks anyone who's not on your list, then it behooves you to put your business correspondents on that list before it becomes an issue. Especially if the correspondence in question is more important to you than it is to them.
That's one reason why I don't use such a filter. I get a lot of email from previously unknown-to-me senders, and some of it ends up being pretty important. At this point, though, I also have a fairly high tolerance for spam (which is good 'cause I get a lot of it), and I know not everyone does. So I can understand the impulse to use a known-senders-only policy. But be aware that if you make your correspondents jump through hoops to send you email, some percentage of them simply won't bother, especially if what they're sending is less important to them than it is to you.