You want to add an IP address to the Office 365 allowed IP list.
Use the O365 Admin interface.
- Log into https://outlook.office365.com/ecp/ with an administrative user
- On the left hand side of the screen select “protection”
- At the top of the screen select “connection filter”
- Double click on the “Default” profile
- On the left side of the Default profile screen select “connection filtering”
- Click the + symbol above the Allowed IP Address details box
- Input your IP Address(s) in the text box one at a time with the following format and click “OK”. IP addresses must be specified in the format nnn.nnn.nnn.nnn where nnn is a number from 0 to 255. You can also specify Classless Inter-Domain Routing (CIDR) ranges in the format nnn.nnn.nnn.nnn/rr where rr is a number from 24 to 32. IPv6 address can be input but messages sent from these addresses will not be accepted by the service.
- Verify that your IP Address(s) are in the Allowed IP Address section by scrolling through it.
- Click Save at the bottom right of the screen