outgoing mail does not work for any of my mail accounts

All of a sudden I cannot send e-mail from apple mail service. I have a verizon account and the iCloud account. At first mail would not go out from either. As I was preparing this request for help the iCloud account sent an e-mail test to my verizon account. The verizon outgoing server still does not work from the apple service. If I go on line to my verizon account I can send my verizon e-mails there. The problem has to be with the apple mail 6.6