iPhones and emails

[MakeItUpAsYouGoAlong]

I email regularly on my iPhone 4 (not a S) and for some reason for the past four days it won't recieve emails. It will however send.
Can anyone give me a insight please

Bump

Have you run out of storage?
Go to settings, general, usage to see how much storage space you have left.

Ahhh I have- what can I do about it?
(Bit clueless at tech)

Easiest thing to do would be to delete some stuff off your phone, any apps you don't use?

Or you could back up your photos and delete some of those?

Thank you