acl based access rules for usernames and email addresses

Issue Summary

hi

i would love to see the option to be able to move the order of the regexpr for restrictions on email addresses and usernames.

for example, i want users to subscribe with a corparate email address (user@example.com) and not with any other email address.

this means something like
allow %example.com
deny %
would do

now if i want to be able to add user@otherfqdn.com as well, i have to delete all rules and start again. where i would like to be able to add
allow %otherfqdn.com
and put this with up/down buttons between the other two options. this way the email regexpresion would work like an accesslist or rulebase; the order is important, cronologic. this way an explicit deny (eg deny %) would be possible as well.

hope this makes sense.