Cannot send emails in new account


New Email

Really hoping someone can help, I am new to this forum!
I have had a account for years but have had to close it as I had to block someone emailing me. Problem is, having set up my new account I cannot send emails, I just compose the email, click send and then I get a message 'Email could not be sent'!!!
I am not at all a techie so please can you explain solution(s) in layman's terms!!! THANK YOU for your help, right now it feels I have left one nightmare for another!!!