Device or application setting
Your MX endpoint, e.g. yourcontosodomain-com.mail.protection.outlook.com
Any email address for one of your Office 365 verified domains. This email address does not need a mailbox.
If you have set up Exchange Hybrid or have a connector configured for mail flow from your email server to Office 365, it is likely that no additional setup will be required for this scenario. Otherwise, create a mail flow connector to support this scenario:
Your organization's email server
Domain restrictions: IP address/range
Your on-premises IP address or address range that the device or application will use to connect to Office 365.
We recommend adding an SPF record to avoid having messages flagged as spam. If you are sending from a static IP address, add it to your SPF record in your domain registrar’s DNS settings as follows:
v=spf1 ip4:<Static IP Address> include:spf.protection.outlook.com ~all