While sending emails from hotmail to cloudflare the below response came.
mx.cloudflare.net rejected your message to the following email addresses: [email protected] ([email protected]) Your message wasn't delivered because the destination email system rejected your message for security or policy reasons. For example, the email address might only accept messages from certain senders, or it might not accept certain types of messages, like those larger than a specific size. Contact the recipient (by phone, for example) and work with them and their email admin to determine what policy or setting blocked your message and what you should do to make sure that future messages from you won't be rejected. For more information, see Status code 5.7.1. mx.cloudflare.net gave this error: 2a01:111:f403:704b::827 isn't allowed to send email for [email protected]. w2yZtQGCgPhc