Exchange refugees often wonder how they can replace the automatic process of populating AD mail fields after they migrate away from exchange. The solution is usually a lot simpler than people expect. You literally just write a value to them.
Here’s a script that lets you pass in a username. It prepends it to your domain name, and it writes it to the Mail field in Active Directory.
Param( [string]$username } Import-Module ActiveDirectory $emailAddress = $username + '@mydomain.com' Set-ADUser -Identity $username -EmailAddress $emailAddress
However you are automating your account creating process, just add this as a step and pass it the username.
If you’re not already automating your account creation process, you would just need to run a script to find new user accounts, and for each new user account, call this script. (See my post on finding new user accounts and my post on scheduling automation tasks).