Apple Mail no longer sending emails
I have a MacBook Pro and have used Apple Mail for years. 2 weeks ago I started receiving this message when sending an email "The sender address .................. was rejected by the server mobile.charter.net." I haven't been able to send an email since then. I can still receive emails. Any ideas as to how to resolve this? I'm very familiar with the SMTP settings I'm supposed to be using.
MacBook Pro