Exchange Online; work on behalf of user: https://outlook.office365.com/ecp/Pickers/EsoPicker.aspx?ActivityCorrelationID=3dec9adf-81ce-1bdc-6cea-efcee3944c50&reqId=1609785679339&pwmcid=1&Launcher=EsoPicker&mode=single

Allows access to setting an auto reply and other basic settings. Useful because you don't have to assign yourself delegate access.

https://security.microsoft.com/tenantAllowBlockList

Allow (specific) external sending infrastructure to spoof specific email addresses in your 365 tenant if they do not support adding a spf/dkim record for their infrastructure