Using email addresses in App Store screenshots
According to the App Store review guidelines, you're responsible for ensuring you own all rights to whatever you put in the description or screenshots.  You can put email addresses in the screenshots but, of course, you need to own those addresses.  You also must be prepared for the onslaught of spam and other email those addresses will receive once the address is displayed to the world.

Common sense would tell me that you should blur at least part of any address you display.  You want to show potential customers an accurate representation of what your app can do.  If that involves displaying an email address, I think you're ok and as long as you blur parts of the address I don't believe Apple will reject it.  If the address is something like xxxx@apple.com or xxxx@yahoo.com, then you should expect a rejection, in part because you're implying that Apple uses or endorses your app as well as you're using a registered trademark.  That is in the review guidelines so it's pretty much a guaranteed rejection.

Just make-up an email address and blur the parts you indicated, you should be ok.