Please see this post in Community & Support about Information on Net ID and system access after graduation. Hopefully it will an answer the questions about your email address. I don’t know how the alumni email address process works.
Just to add to Paul’s reply. There is specific information in the link he provided that discuss your UW-Madison system access after graduation, and also links on how to setup a free alumni email address through he UW Alumni Foundation. Let us know if you have other questions.
Unless I am missing it I am not seeing specifically if our current @wisc email goes away. I am referencing the table on the Deactivation Timeline KB page.
Your UW email access will not end, so it is not listed on that deactivate timeline. Please refer to the section on the KB page for Email Service options, this will explain more about your continued UW email, and also about obtaining a UW Alumni email address if you want it.