Some example emails:
Etc. Banning these emails, make it so people can not use temporary email addresses to sign up to my form for a quick fix or to spam it etc. This also ensures that my mandrill account does not end up sending emails to fake addresses causing it to get a poor rating.
I'm surprised this is not already an option considering the amount of things you can already import / export on the ACP.
A good reason for allowing this to be exported and important is simply because, it makes things much easier than having to add hundreds of emails one by one.
This could also help users of XenForo, for us to share our email lists, and users can import them in a few clicks.