My email has stopped sending, receiving is ok. Not changed any settings... Just all of sudden won't send mail. Please hel

HI guys, please can you help.

All of a sudden (Yesterday) my email has stopped sending from my account. when I go to check the iCloud settings, a message is displayed stating that iCloud cannot connect to the server, yet I can still receive mail, very frustrating.

I Have not altered any settings. apple say the server is up and running so i am puzzled. Any assistance will be greatly appreciate.

Many thanks