Is TurboTax @em1.TurboTax.com legit?

Yes, it is legit. 

I E-filed our tax returns on May 1st and since then have received two emails (one yesterday) telling me that I still need to sign the return and to click on a box to open TurboTax and finish the return. I checked with the IRS web site and they have received the return. Why does TurboTax still think I need to finish this return?

Yes. It is legit and it refers to State taxes for 3 states. California, Alabama and Georgia. I wish the reminder was smart enough to only send it to folks who had income in those 3 states instead of sending it to all users.