The settings should be mobile.charter.net on port 993 for the incoming IMAP, and port 587 for the outgoing SMTP. Security = SSL/TLS, authentication = normal password, and User Name = email address. https://support.mozilla.org/en-US/questions/1234783#answer-1157069 https://www.spectrum.net/support/internet/email-troubleshooting?redirected=true For the outgoing, first select SSL/TLS for the security, then type 587 in the port box, as most servers use port 465. Delete any obsolete passwords in Tools/Options/Security/Passwords/Saved Passwords.