mail notifications and limit request with a token

Issue Summary

This module is great, btw I would require 2 enhancements:

1) mail notifications when a user signup (with enable/disable options)
2) a possibility to write a fixed token max times for a signup, (with enable/disable options) for example:
For a signup I write:
"blabla@blabla.com myToken" (quotes for clarity only) and after 200 requests of this type (with "myToken" as suffix) the users get an error when they request a signup

thanks you
bye