Trouble With My Ntlworld mail on my iPhone 4 HELP PLEASE

[Irishdancer]

I have a iPhone 4 with o2 it all my emails stopped working got all the others to work not ntlworld I put in the right email and pass work for out going mail pop3.ntlworld.com out going mail smpt.o2.co.uk do not know how to see if it is on the port so can some on on here HELP ME PLEASE