PowerShell script to bulk add new email aliases to Active Directory users

The basic update is fairly simple, but the risky part is assuming names are unique. People can share the same first and last name, and some accounts may already have conflicting aliases. Build in validation, produce an exception report, and don’t automatically update rows that fail those checks.

The right command depends on the environment. With on-premises Exchange, an email address policy may be able to apply the format automatically. In a hybrid or cloud-managed setup, the authoritative attribute and update command can be different, so confirm where mailbox addresses are managed before modifying Active Directory directly.

Make a couple of test users or a small pilot group first, then verify that the new address appears correctly and that mail delivery still works. Once the output is confirmed, run the bulk update with logging so you have a record of every successful change and every skipped account.

I’d start by exporting the target users to CSV, generate the proposed alias in a separate column, and review the results before changing anything. Check both duplicate generated addresses and aliases that already exist elsewhere. Once the file looks correct, use it as the input for the update script and test with a small group first.