Script to Resolve Error When Running Enable-RemoteMailbox

If you have existing user accounts in your hybrid environment, and want create a mailbox in Office 365 for those users, you can use the Enable-RemoteMailbox cmdlet. However, when you try to use Enable-RemoteMailbox you commonly get the following error:

The address '@yourtenant.mail.onmicrosoft.com' is invalid: "@yourtenant.mail.onmicrosoft.com" isn't a valid SMTP address. The domain name can't contain spaces and it has to have a prefix and a suffix, such as example.com.

This error occurs because the cmdlet is not building the RemoteRoutingAddress properly. This address is used for routing messages to the Office 365. So, we need to create that RemoteRoutingAddress property as part of a piped command or script.

I've seen several examples using piped commands, but I prefer a script because I find it easier to follow the logic. Here is the script I used recently:

$users = get-user -OrganizationalUnit "OU=xx,DC=domain,DC=com" -RecipientTypeDetails User 

foreach ($u in $users) {
   $alias = $u.FirstName + "." + $u.LastName
   $RR= $alias + "@yourtenant.mail.onmicrosoft.com"
   Enable-RemoteMailbox -identity $u -RemoteRoutingAddress $RR
}

This script obtains a list of users without mailboxes from a specific OU. Then it loops through that list of users, takes user properties to build the remote routing address in the variable $RR. Finally it enables the remote mailbox for each user.

When you use the Enable-RemoteMailbox cmdlet, it also automatically adds that remote routing address as an email address for the account. Which is of course required for Office 365 to accept the mail.