Hey Guys, I came here to share my experience I was having major issues adding my exchange e-mail through the native mail app server
I was getting the 'Cannot Get Mail - the connection to the server failed.'
What I realized once signing into the Outlook WebMail app for my exchange e-mail is it allows a total of THREE mobile connections. Meaning if you had phones previously or have added multiple backups what not, it creates a 'new connection'.
After three connections, it blocks you from pulling the e-mail from the server. Meaning, you can add and it shows successful but won't pull the e-mail.
What I did was delete all my mobile phone connections through the Webmail app ----> Signed out ----> Re-added the e-mail via my iPhone.
To access the mobile connections through Outlook WebMail:
Login > Options > Phone > Mobile Phones
Again, this is only for Exchange e-mails. This worked for me. Hopefully, it helps someone out.