@scottvoth – I did not receive the at-mention email. Weird.
Anyway, what Matt states is correct. The “Email notice” function is meant to be used for rudimentary, occasional email blasts and is not meant to be recorded in the group activity stream.
If you need something posted in the group activity stream, then you should ideally create a new forum topic in your group like Matt mentions above.
The “email notice” feature was coded by another developer on the Group Email Subscription plugin and is really only ideal for small working groups. If you have a rather, large group this functionality probably won’t scale well.