To troubleshoot the issue of emails, here are steps to fix the Cox SMTP server issue, which is a major reason why you have such an issue:
Make sure the server settings below match your Cox email account on the device you are using.
Sometimes issues arise due to a poor network connection. Check your internet connectivity.
You should also check your credentials, such as your username and password. If they are wrong, you have to enter the correct details.
Ensure that the account type is set to IMAP.
Make sure TLS or SSL is enabled.