It can be sent now, but the email was not received
root@iZ0jlfiypegsmh5fpig7t4Z-app:/var/www/discourse# rake emails:test[whitewatercn@outlook.com]
Testing sending to whitewatercn@outlook.com using in-v3.mailjet.com:587, username:7b14af9b5034dd6e7639d19587cb7831 with plain auth.
SMTP server connection successful.
Sending to whitewatercn@outlook.com. . .
Mail accepted by SMTP server.
Message-ID: fc301347-746b-4b89-8c07-deeb1ee467a4@discuss.whitewater.wang
If you do not receive the message, check your SPAM folder
or test again using a service like http://www.mail-tester.com/.
If the message is not delivered it is not a problem with Discourse.
Check the SMTP server logs for the above Message ID to see why it
failed to deliver the message.