Email problem on I Phone 6

Hi there, I have an Iphone 6 with IOS 9.2.1 (13D15), model MG4J2B/A which I have 5 separate email accounts on. Two of them are via VirginMedia, one is for work and one is Personal.

My business one does not allow me to reply to emails on my phone which is becoming annoying. The other virginmedia one is fine and I have to forward the email to the other to reply/send. It says the user name and or password is not correct.

I have tried a few times deleting both accounts, and reinstalling - no solution.

I have changed the password, again no solution.

I am receiving emails fine on my laptop so cannot understand why I can't get it to work on my phone!

Any suggestions gratefully accepted,

Many thanks

Suzanne