Problem sending mail

As of Tuesday, I am unable to send mail. All outgoing mail ends up in Outbox. I can receive mail just fine. When sending I get this message: Cannot send message using server charter.net. Connections to the server "mobile.charter.net" on the default ports timed out. Select a different outgoing mail server from the list below or click Try Later to leave the message in your Outbox until it can be sent.

Edit SMTP Server List includes: Charter.net (offline) iCloud

Connection Doctor shows that our three email accounts (IMAP) - Connection and login to server succeeded

But charter.net SMTP is unable to connect.

Could not connect to this SMTP server. Check your network connection and that you entered the correct information in the Account preferences. Also verify that server supports SSL. If it does not, deselect the "Use TLS?SSL" checkbox in the Server Settings Tab of Account preferences.

I have been using apple mail for the past 6 years on this machine without a problem. This problem seemed to pop up on its own early this week.