Emails won't download from server

My Mail app has all of a sudden stopped downloading my emails. once I open the app I can see all my emails and the two first lines of my emails, but the moment I click to open an email it says "This message has not been downloaded from the server".

I have tried resetting my phone, deleting my account and then re-entering it, I have tried resetting my networks, deleting and re-downloading the Mail App itself, turning my phone on and off and it still refuses to load. I have tried on WiFi with data off, on data with WiFi off and my emails still show up saying "This message has not been downloaded from the server" once I open them.

I can access my Hotmail account by going through the Safari/Google app and all my emails load perfectly. It seems to only be an issue when I try to open my emails through the Mail app that.

If anyone has any ideas on what is happening or how to fix it, I would be forever grateful!

Thank you.