My iPhone reverted to previous settings / passwords

I uploaded a playlist from iTunes onto my phone and it messed up the settings! It has also erased emails dating after 2015. What do I do?!

ITunes needs a lot of work, and when it does something weird like that, it's hard to get it back the way you had it.

But it would never mess with your Email app.

? What? I find it hard to believe that an iTunes playlist had anything to do with your e-mail… Truth up… What did you do?