If you are dealing with Cox email not sending on Windows 10, then check out the steps:
Check the email in other folders with Cox email that includes trash and spam folder.
Check Cox email account filters and see if the new incoming email is not being filtered out.
Ensure that you have not blocked the recipient.
Also, make sure that the sender does not block you.
Check the POP and IMAP settings, and you can’t even send an email if the Cox email SMTP server is not working.
Lastly, disable the antivirus software installed on your device.
Try to send an email to yourself; if you don't receive an email in your inbox, it states that Cox email is facing trouble or not working properly.
Check your email in other folders within Cox email accounts that include spam, trash, etc.
Along with it, check the filters of the Cox email account and check if the new incoming emails are not being filtered out.
Ensure that you have not blocked the sender or recipient.
Also, make sure that the recipient or sender does not block you.
Check for the IMAP/ POP configuration settings. Keep in mind that you can't send an email if the Cox email SMTP server is not working.
Lastly, disable the antivirus software temporarily, which is installed on your device.
Hope This Helps,
Peter