I certanly dont recommend this but this is what worked ….
$User = ""
$Users = ""
$Users=Get-ADUser -filter * | select SamAccountName
foreach ($User in $Users)
{
set-ADUser -identity $User.SamAccountName -clear legacyExchangeDN
set-ADUser -identity $User.SamAccountName -clear mailNickname
set-ADUser -identity $User.SamAccountName -clear msExchHomeServerName
set-ADUser -identity $User.SamAccountName -clear msExchMailboxGuid
set-ADUser -identity $User.SamAccountName -clear msExchMailBoxSecurityDescriptor
set-ADUser -identity $User.SamAccountName -clear msExchPoliciesIncluded
set-ADUser -identity $User.SamAccountName -clear msExchRBACPolicyLink
set-ADUser -identity $User.SamAccountName -clear msExchRecipientDisplayType
set-ADUser -identity $User.SamAccountName -clear msExchRecipientTypeDetails
set-ADUser -identity $User.SamAccountName -clear msExchTextMessagingState
set-ADUser -identity $User.SamAccountName -clear msExchUMDtmfMap
set-ADUser -identity $User.SamAccountName -clear msExchUserAccountControl
set-ADUser -identity $User.SamAccountName -clear msExchUserCulture
set-ADUser -identity $User.SamAccountName -clear msExchVersion
set-ADUser -identity $User.SamAccountName -clear proxyAddresses
set-ADUser -identity $User.SamAccountName -clear showInAddressBook
}