Using Office 365 Exchange Online, how to relay e-mail for equipment such as copier!!
  1. Admin Portal > Exchange Admin Center > Mail Flow > Connector > Add New Connector
  2. From select “Your organization’s email server” and to select “Office 365”
  3. Assign a name and description for connector
  4. Enter the domain or IP address permitted to use this connector (*1)
  5. Done!
SMTP Server address is MX record target name
Remark: not allow to using IP address as SMTP host
Port is 25 without SSL/TLS is ok (Jacky tested)
Final you need to setup SPF record add the permitted IP address, else your relay mail may classify is spam.