Why did my icloud email account disappear from my iphone overnight?

Hello, woke up this morning and the icloud email account was no longer showing on my iphone. The icloud account is still registered on my phone in settings and other things (contacts and calendar) are synching fine. It's only the emails I can't get. The other thing, in settings>Mail,etc>icloud>the account name (my email address is greyed out, as is the email address under "icloud account information" and "allow sending from".

Any help to get my emails back on my phone would be great! Thanks