I get the following message when I attempt to send email during the same three hour window everyday.
Task 'email@example.com - Sending' reported error (0x800CCC67) : ' The server responded: 421 p3plsmtpa07-03.prod.phx3.secureserver.net MTPAUTH: IP XX.XX.XXX.XXX rejected for too many failed logins. Please check any clients or devices that may be misconfigured, and try again later.'
I blanked out my email address and the ip address fro security. The ip address is registered to Time Warner. Thanks for any ideas someone might have.