I can't use my e-mail account because there is something wrong with it. Every time I try to use it, it says:

The host 'SMTP' could not be found. Please verify that you have entered the server name correctly. Account: 'POP3', Server: 'SMTP', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Error: 11001, Error Number: 0x800CCC0D

how do I fix this?

You need to check what the outgoing SMTP server is set for and make sure its correct. If it is, contact your ISP since it may be a problem on their end.