I've changed the email delivery settings for a user on my server and when I perform a test I'm seeing this weird error in the log.
2020-03-29 14:27:27.063 Error App: Error sending email: System.Net.Mail.SmtpException: Service not available, closing transmission channel. The server response was: Cannot connect to SMTP server ::ffff:22.214.171.124 (::ffff:126.96.36.199:25), connect error 10060
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw(Exception source)
at System.Net.Mail.SmtpConnection.ConnectAndHandshakeAsyncResult.End(IAsyncResult result)
at System.Net.Mail.SmtpTransport.EndGetConnection(IAsyncResult result)
at System.Net.Mail.SmtpClient.ConnectCallback(IAsyncResult result)
--- End of stack trace from previous location where exception was thrown ---
" The server response was: Cannot connect to SMTP server ::ffff:188.8.131.52 (::ffff:184.108.40.206:25) "
I've double checked the host servers DNS cache, performed a ping, and the right IP address resolves. I'm not sure where the " ::ffff: " part is coming from. I've changed the settings and even tried restarting the server. Looking for some other suggestions or guidance.