Cox has sending limits in place for outbound email. These limits are intended to reduce the amount of unwanted spam on the Internet by identifying and containing “spam bot” attacks generated from Cox customers’ PCs. These limits are set very high, and it is unlikely that normal residential mailings will surpass the limits. Cox has chosen sending limits based on other ISP’s best practices and analysis of existing email traffic to insure even large legitimate residential mailings complete with no errors.
Please resend your message using Cox Webmail instead of your current email utility (https://myemail.cox.net). I successfully sent an email to 10 recipients this morning using my Cox Webmail account.