There’s no shortage of how-tos out there for this topic, but if you want the copy-and-paste method, this is all there is to it:

1. Login to your Office 365 account and enable Rights Management: https://docs.microsoft.com/en-us/information-protection/deploy-use/activate-office365-preview
2. Open PowerShell as AdministratorAssuming you’re in North America, and you want to encrypt all messages with ‘secure’ in the subject, run:

   $UserCredential = Get-Credential
   $Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection
   Import-PSSession $Session
   Set-IRMConfiguration -RMSOnlineKeySharingLocation “https://sp-rms.na.aadrm.com/TenantManagement/ServicePartner.svc”
   Import-RMSTrustedPublishingDomain -RMSOnline -name “RMS Online”
   Set-IRMConfiguration -ClientAccessServerEnabled $false
   Set-IRMConfiguration -ClientAccessServerEnabled $false
   Set-IRMConfiguration -InternalLicensingEnabled $true
   New-TransportRule -Name ‘Encrypt on “secure” in subject’ -Comments ‘ ‘ -Mode Enforce -SubjectContainsWords ‘secure’ -ApplyOME $true

3. Wait a few hours for Rights Management to really be enabled, then try sending test messages until they’re encrypted.