Add BYU's student-body-only email domain.

My apologies for my incorrect submission last time. This is the domain only active students can have, @studentbody.byu.edu.

Reference:
https://it.byu.edu/byu/BYU+Help+Center+Article.do?&sysparm_document_key=kb_knowledge,b4f139670a0a3c0e77251228591c8f0d