Get AD Group Members, manipulate samAccountname, and then add to distribution list.

TJCooper 

Hi there.

I'm making some assumptions here as it's not entirely clear if you are talking about Active Directory and Exchange Server, Azure Active Directory and Exchange Online, some combination of the two (hybrid), or whether there's any write-back from Azure Active Directory to Active Directory (only relevant in a hybrid scenario.)

For the following example, I've made the assumption that you're talking about Active Directory and Exchange Server, but if you can provide some clarity on your environment, we can potentially provide a more appropriate example.

Example

$DistributionList = "Some Name";

Get-ADGroupMember -Identity "Domain Users" |
    Where-Object {
        # This is where we filter out anything that doesn't begin with the prefix we're interested in.
        ($_.objectClass -eq "user") -and ($_.sAMAccountName -like "SA-*");
    } |
    ForEach-Object {
        $sAMAccountName = $_.sAMAccountName.Substring(3);

        if (($Results = Get-ADUser -Filter { (sAMAccountName -eq $sAMAccountName) -and (mail -like "*") } -Properties mail) -is [Microsoft.ActiveDirectory.Management.ADUser])
        {
            # If we're in here, we received exactly one match.
            Add-DistributionGroupMember -Identity $DistributionList -Member ($Results.mail);
        }
        elseif ($Results -is [System.Object[]])
        {
            # Outside of replication conflict scenarios, we should never end up in here.
            Write-Warning -Message "Searching on $sAMAccountName returned multiple matches.";
        }
        else
        {
            # If we're in here, nothing matched.
            Write-Warning -Message "Searching on $sAMAccountName returned no matches.";
        }
    }

Cheers,

Lain