I have check and double checked what more can I check

I am trying to use the E-newsletter and I am doing a test send but when I try and send a newsletter I keep getting
error sending email please check outgoing email settings

I have checked the setting many times and cant find anything wrong
I have also tested the connection in the settings and I get a test message sent you can save your settings but when I send a news letter it gives an error sending email please check outgoing email settings.