Can't receive verification mail from some web services

Can't receive verification mail from some web services

Hello.

I set up my email address with custom domain. I send mails to the address from my other addresses (gmail and protonmail) and I successfully received test messages in zoho inbox.
However, I tried to register GitHub and Google with a new email address and I couldn't find incoming messages from GitHub or Google. GitHub seems to send mails via SendGrid.

What should I do?