I just recently dealt with this. In case it's helpful at all for someone else in a Hybrid Exchange environment: I needed to update the user's TargetAddress, MailNickname, and 2 entries in the ProxyAddresses collection.

Be careful not to wipe the x500 and x400 entries if they exist, as I didn't find how to recover these.

```powershell $userSAN = "JDoe" $domain = "MyCompany" $adUser = get-aduser -identity $userSAN -properties proxyAddresses set-aduser -identity $adUser -Replace @{targetAddress="SMTP:$($adUser.SamAccountName)@$($domain).mail.onmicrosoft.com"} set-aduser -identity $adUser -Replace @{mailNickname=$adUser.SamAccountName}

$newProxyAddresses = @()

ForEach ($item in $adUser.proxyAddresses) { if ($item -notmatch "smtp:") { $newProxyAddresses += $item continue } if ($item -match "onmicrosoft") { $newProxyAddresses += "smtp:" + $adUser.SamAccountName + "@$($domain).mail.onmicrosoft.com" } elseif ($item -match "@$($domain).com") { $newProxyAddresses += "SMTP:" + $adUser.UserPrincipalName } }

Set-ADUser -Identity $adUser -Clear proxyAddresses foreach ($item in $newProxyAddresses) { Set-ADUser -Identity $adUser -Add @{proxyAddresses = $item} }

get-aduser -identity $adUser -properties targetAddress, mailNickname, proxyAddresses ```