I would like to get a report for IP addresses from were user's have singed in either using outlook or OWA in last 1 month.
I've tried Audit log search on exchange admin center but could not find anything. Is there anything else I can do to get the list?
Um, wrong title?
Use the Audit log functionality in the Security and Compliance Center: https://protection.office.com/#/unifiedauditlog
You will have to enable Owner-level auditing on the mailboxes first though. Alternatively, you can look at the Sign-In events for Azure AD and filter out those related to Exchange.