When i try to accept or transfer email I am told that the host cannot be found?

I have no idea what my granddaughter has done to my computer, I have trouble sending and transferring, receiving emails. I am frequently told that the host cannot be found. The host name is calico. My granddaughter's name is Callie. I cannot receive e-mails or send e-mails to places like Craig's list and other places. How do i fix this problem? I cannot answer e-mails from classified addsI try to send out e-mails and an erro message comes up and says, "the host 'callie minton' could not be found. Please verify that you have enered the server name correctly. Subject 'Emailing:23358_1516160986908_1320966666… Account: 'callici@yahoo.com', Server:'callie minton', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Erroe:11001, Error Number: 0x800CCCOD.