Hello Guys. How do i block malicious senders in office 365 security and compliance?

Tata1980 

You can block the Ip or IP range using connection filter … refer below article

https://docs.microsoft.com/en-us/office365/securitycompliance/configure-the-connection-filter-policy

To block the domain or sender.. use Anti Spam policy or create a transport rule.. refer below article..

https://docs.microsoft.com/en-us/office365/securitycompliance/create-block-sender-lists-in-office-365

Thanks

Robin Nishad

Sr Consultant