Send mail via SendGrid to Outlook was always failing

Question

I am a newbie in using SendGrid. I have a web application that send a mail to users after the successful registration. I am using send grid to send mails.

It works fine when I try to send Google email accounts. But when I send mails to Outlook email addresses, it always failed to deliver emails.

I checked the SendGrid 'Activity' section it shows like below.

Answer 1

You might need to setup domain authentication. This link should be a good place to start: https://sendgrid.com/docs/ui/account-and-settings/how-to-set-up-domain-authentication/

Outlook might have different firewall rules blocking incoming (potentially malicious) emails while GMail might have a different set of them.