Announcing: Office 365 endpoint categories and Office 365 IP Address and URL web service

ankit1990 Do you have a hybrid Exchange configuration that includes on-premises Exchange servers or some other on-premises SMTP email server at your offices or your datacenter locations? If you do not, then any email delivered from a US address tenant to an India tenant will be delivered within Office 365 infrastructure and does not get sent outside of Microsoft's network. If you do have this, then you can filter SMTP email using your firewall but Microsoft does not provide a way to identify user or tenant locations by SMTP source IP Address.

SMTP blocking is not the right way to do mail filtering in Office 365, I'd recommend you read about Exchange Online Protection here https://docs.microsoft.com/microsoft-365/security/office-365-security/exchange-online-protection-overview 

Regards,
Paul