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Add Email alias to O365

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Bychris_fry

To set an email alias in the Active Directory (AD) Attribute Editor, edit the proxyAddresses attribute on the user object, adding the new email in lowercase smtp:alias@domain.com format. Ensure “Advanced Features” is enabled in AD Users and Computers (ADUC) to view the Attribute Editor. Changes will sync to Microsoft 365 within 30 minutes to an hour. 

Steps to Set SMTP Alias:

  1. Open ADUC: Open “Active Directory Users and Computers” and ensure View > Advanced Features is checked.
  2. Locate User: Find the user, right-click, and select Properties.
  3. Attribute Editor: Navigate to the Attribute Editor tab.
  4. Edit proxyAddresses: Locate proxyAddresses, double-click it (or click Edit).
  5. Add Alias: In the value box, type smtp:newalias@yourdomain.com (lowercase ‘smtp’ is critical for an alias).
  6. Save: Click Add, then OK.
  7. Sync: Wait for AD Connect to synchronize changes, or run a delta sync via PowerShell using Start-ADSyncSyncCycle -PolicyType Delta.

Key Considerations

  • Primary vs. Alias: The primary email address uses uppercase SMTP:user@domain.com, while secondary aliases use lowercase smtp:alias@domain.com.
  • Hybrid Environments: For synced environments, you must make these changes in your on-premises AD, not in the Microsoft 365 admin center.
  • Validation: If the alias already exists elsewhere, the synchronization will fail.