Problem after removing arbitration mailbox using ADSIEdit

If you removed the arbitration mailbox from ADSI and not via EMS (Here’s how to use EMS) you may get the following errors when trying to reinstall the mailbox role.

Log Name: Application
Source: MSExchangeSetup
Event ID: 1002
Task Category: Microsoft Exchange Setup
Level: Error
Keywords: Classic
User: N/A

Exchange Server component Mailbox Role failed.
Error: Error:
The following error was generated when "$error.Clear();
if ($RoleIsDatacenter -ne $true)
{if (test-ExchangeServersWriteAccess -DomainController $RoleDomainController -ErrorAction SilentlyContinue)
{# upgrade the discovery mailboxes to R5 version, this will fix the RecipientDisplayType property of the discovery mailbox which was wrong in R4.
get-mailbox -RecipientTypeDetails DiscoveryMailbox -DomainController $RoleDomainController | where {$_.IsValid -eq $false} | set-mailbox -DomainController $RoleDomainController
$name = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxUniqueName;
$dispname = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxDisplayName;
$mbxs = @( get-mailbox -Filter {name -eq $name} -IgnoreDefaultScope -resultSize 1 );
if ( $mbxs.length -eq 0)
{$dbs = @(get-MailboxDatabase -Server:$RoleFqdnOrName -DomainController $RoleDomainController);
if($dbs.Length -ne 0)
{$mbxUser = @(get-user -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1);
if ($mbxUser.Length -ne 0)
{enable-mailbox -Discovery -identity $mbxUser[0] -DisplayName $dispname -database $dbs[0].Identity;}}}}
else
{write-exchangesetuplog -info "Skipping creating Discovery Search Mailbox because of insufficient permission."} }

Active Directory operation failed on server.domain.local. This error is not retriable. Additional information: The name reference is invalid.
This may be caused by replication latency between Active Directory domain controllers.
Active directory response: 000020B5: AtrErr: DSID-03152392, #1:0: 000020B5: DSID-03152392, problem 1005 (CONSTRAINT_ATT_TYPE), data 0, Att 200f4 (homeMDB)

Normally this error indicates a problem contacting a DC or the Server not being in the “exchange servers” AD group, in this specific instance this can be caused because the discovery mailbox missing the HomeMDB and HomeMTA attributes.

Here is how to manually add them back

Start –> Run –> ADSIEDIT.MSC (should already know this since you used it to remove the MBX)
Default Naming Context –> “DC=Domain, DC=Local” –> CN=Users –> CN=DiscoverySearchMailbox {}
Right Click –> Properties
Find HomeMDB and HomeMTA this needs to be populated with the DN of the server and Database.