Tag Archives: Exchange Online

Exchange Online, Office365, Security

Mimecast trust cert hacked in Microsoft supply chain

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The Threatpost.com and other cyber security news published articles claiming that A Mimecast-issued certificate used to authenticate some of the company’s products to Microsoft 365 Exchange Web Services has been “compromised by a sophisticated threat actor,” the company has announced.

Office 365 Products and Services Explained

Mimecast provides email security services that customers can apply to their Microsoft 365 accounts by establishing a connection to Mimecast’s servers. The certificate in question is used to verify and authenticate those connections made to Mimecast’s Sync and Recover (backups for mailbox folder structure, calendar content and contacts from Exchange On-Premises or Microsoft 365 mailboxes), Continuity Monitor (looks for disruptions in email traffic) and Internal Email Protect (IEP) (inspects internally generated emails for malicious links, attachments or for sensitive content).

A compromise means that cyberattackers could take over the connection, though which inbound and outbound mail flows, researchers said. It would be possible to intercept that traffic, or possibly to infiltrate customers’ Microsoft 365 Exchange Web Services and steal information.

Reference:

https://threatpost.com/mimecast-certificate-microsoft-supply-chain-attack/162965/

https://www.crn.com/news/security/hackers-compromise-mimecast-certificate-for-microsoft-authentication

Exchange Online, Office 365, Office365, Powershell

Upgrading Exchange Online PowerShell to V2 Module

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Managing Exchange Online

If you have Exchange Online and your users are MFA enabled then you most likely will be using Exchange Online’ s ECP (Exchange Control Panel or Admin Center) to connect to Exchange Online PowerShell through the Hybrid Windows since this is the only supported way with MFA.

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Clicking on Configure would install the PowerShell Module of Exchange Online which looks like the below screenshot.

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New PowerShell with MFA support

If you have launched Exchange Online PowerShell today then you most likely have noticed there’s a red line stating the possibility to try the new (Preview Version) of Exchange PowerShell V2 .

Microsoft has recently released a new version of Exchange Online PowerShell Module which supports MFA and can be run directly from your computer without the need to login to Exchange Online Admin Center and download any files from there.  Check details in this link

As stated in the article, the Module is just in preview so it has some known and maybe unknown bugs as well.

How to Install it?

The installation process is pretty straightforward, Launch Windows PowerShel as an Administrator (It’s required for the installation).

Run these 4 cmdlets

Set-ExecutionPolicy RemoteSigned

Install-Module PowershellGet –Force

Update-Module PowershellGet

Install-Module -Name ExchangeOnlineManagement

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You might get a warning that the Module you’re about to install is from an Untrusted Repository, Accept it by typing Y and hit enter

Type the following cmdlet to ensure that Exchange Online Management module is installed

Import-Module ExchangeOnlineManagement; Get-Module ExchangeOnlineManagement

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Connecting to Exchange Online

To connect to Exchange Online, Run the following cmdlet along with the new parameter –EnableErrorReporting which gives the ability to record all the cmdlets that you have run along with errors generated as well.

Connect-ExchangeOnline -EnableErrorReporting -LogDirectoryPath e:\ExchOnlineLogs.txt -LogLevel All

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After connecting, I am going to try and run two commands the Old Cmdlets and New Cmdlet and see the difference between them:

  1. Get-CASMailbox -ResultSize 10
  2. Get-EXOCasMailbox -ResultSize 10

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The new Cmdlet has much more details, although it says that it runs faster but it took few seconds more than the old one to run (Probably first time).

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After you run those two Cmdlets, There will be two files generated in the log directory which we have pointed the parameter to save files to.

The CSV files have details about the two cmdlets and the HTTP Method they are utilizing in order to connect along the Request and response latency.

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This new version seems to be extremely useful esp in environments where such deep details are needed for troubleshooting issues.

Stay tuned for more

Reference:

https://docs.microsoft.com/en-us/powershell/exchange/exchange-online/exchange-online-powershell-v2/exchange-online-powershell-v2?view=exchange-ps

Active Directory, Exchange 2016, Exchange 2019, Exchange Online, Microsoft, Office 365, Powershell

How to Sync Cloud User to On-premises AD ?

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The Story:

I have got this client who constantly keeps on making the mistake of create user from Cloud and provision them with a license in an Exchange Hybrid environment.

Although this is not difficult to fix but it’s not the recommended approach when creating a new user especially in a Hybrid environment since Exchange on-premises won’t recognize this user and most likely will consider any incoming emails from it as spoof or spam.

How to Create a Cloud user from Exchange On-premises?

From Exchange on-premises ECP Admin panel you have the option to directly create user on-cloud which will also create a user object on on-premises AD.

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Second option – Using Powershell

It’s not that much different than the Web UI option but it’s just for people who prefer using PowerShell than GUI

Enable-RemoteMailbox –Identity User –RemoteRoutingAddress user@yourTenant.mail.onmicrosoft.com

The reason to follow those two methods is due to the need of Exchange on-premises being aware of each of those users so mail flow between Exchange on-premises and Online would not get affected and route this users mail to the wrong place or flag it as spammed or spoof …etc.

The Real Question now is: How to Sync Cloud User to On-premises AD ?

If by mistake we created a user on Cloud (Office 365) and we forgot to create an AD User for this account, that user might already have started using his account on Office 365 (Sharepoint, Exchange, Teams) etc.

There also might be the intention of moving users from Cloud to On-premises Exchange in case the company wanted to decrease their spending on cloud users and in this case when Migrating a cloud user to on-premises you will get the following errors:

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test3@domain.com

Status: Failed

test3@domain.com Skipped item details

User status

Data migrated:

Migration rate:

Last successful sync date:

Error: MigrationPermanentException: Cannot find a recipient that has mailbox GUID ‎’03c9764e-8b8e-4f33-94d1-ef098c4de656‎’. –> Cannot find a recipient that has mailbox GUID ‎’03c9764e-8b8e-4f33-94d1-ef098c4de656‎’.

So how do we overcome this situation since syncing a user might require you to delete the cloud user and recreate it on AD?

Solution:

To sync the user from the Cloud to on-premises you will need to follow these steps :

1- Create an on-premises Mailbox where the following attributes would be matching the cloud user

  • UserPrincipalname
  • ProxyAddresses
  • SamAccountName
  • Alias

2- The Location of the OU where the On-premises user is going to be created must be provisioned by ADConnect (Azure AD Connect)

You can look which of these OU are provisioned by Starting AD Connect Sync Manager

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By verifying the user you created in the AD is in the right OU, You can now start AD Sync from PowerShell to speed up the process.

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Below, You can see the user has been successfully synchronized to the cloud without any issue.

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Now we’ll see it from the portal to confirm the user is synced with AD

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Depending on the Source anchor being used in ADConnect there might be a GUID conflict or not, You will get an error similar to when trying to migrate the user in the beginning however you can solve this by replacing the cloud user’s GUID (ImmutableID) with the on-premises user which will force the user to merge with the On-prem user.

Let’s confirm in our case if the user on-cloud has a matching GUID with the one on-premises.

From CMD or Powershell you can use the following command to get the user’s ImmutableID (ObjectGUID) .

ldifde -f c:\Test.txt -d “cn=Test3,DC=Domain,DC=com”

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Checking the notepad we just exported you can see the Immutable ID on AD for the User test3 is IkTni9mw7Ee4YefeGpz7IA==

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To be able to see the user on Office 365, We need to logon to MSOL through Exchange Online powershell

Connect to Exchange Online’s powershell using your Online ECP.

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Once you click on Configure this should download an executable file that will launch PowerShell Online which allows you to use the Modern Authentication (MFA) to use PowerShell safely.

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Connect-Msoluser will connect you to Office 365 and you’ll be able to get the user’s properties and see if the Immutable ID is matching to the user’s GUID.

Once you’re connect you can use the following cmdlet to get the user’s properties.

Get-MsolUser -UserPrincipalName test3@domain.com |fl DisplayName,ImmutableID

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You can see they are matching each other, In case there’s a conflict then you can simply set the online user’s Immutable ID to the on-premises user and that should solve the problem.

Ref:

https://support.microsoft.com/en-us/help/2956029/migrationpermanentexception-cannot-find-a-recipient-that-has-mailbox-g

https://docs.microsoft.com/en-us/exchange/hybrid-deployment/create-cloud-based-archive

Exchange 2016, Exchange 2019, Microsoft Exchange, Office365

Search and Delete certain Items/Folders from a Mailbox

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The Story

During a project of Hybrid migration from Exchange on-premises to Exchange online, I was almost about to finalize the project by moving the last remaining users mailboxes however had an interesting issue to deal with where a user was failing with the following error:

Error:

Error: MigrationPermanentException: Mailbox dumpster size 50.87 GB (54,620,074,576 bytes) exceeds target quota 30 GB –> Mailbox dumpster size 50.87 GB exceeds target quota.

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After some research it turned out that you can clean the dumpster using search-mailbox PowerShell cmdlet, Sync the user’s object with ADConnect and then continue the migration from the last failure.

To solve the issue, Go on your Exchange on-premises and launch Exchange Management shell

Solution:

First, Let’s see the user’s dumpster and recoverable items

Get-MailboxFolderStatistics -Identity “User” -FolderScope RecoverableItems | Format-Table Name,FolderPath,ItemsInFolder,FolderAndSubfolderSize

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To Delete the dumpster only use this

Delete dumpster only

Search-mailbox -identity User -SearchDumpsterOnly –DeleteContent

To delete a certain email with certain subject in the dumpster use the following:

Get-mailbox “user”| search-mailbox –searchquery “Subject:’*'” –DeleteContent –SearchDumpsterOnly

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The cmdlet will search and delete

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Reference:

https://docs.microsoft.com/en-us/microsoft-365/compliance/search-for-and-delete-messagesadmin-help

Exchange 2019, Microsoft Exchange, Office 365

MRSPROXY.SVC’FAILED BECAUSE NO SERVICE WAS LISTENING ON THE SPECIFIED ENDPOINT. THE REMOTE SERVER RETURNED AN ERROR: (404) NOT FOUND

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Symptoms

MRSPROXY.SVC’FAILED BECAUSE NO SERVICE WAS LISTENING ON THE SPECIFIED ENDPOINT. THE REMOTE SERVER RETURNED AN ERROR: (404) NOT FOUND

You get an error when you’re trying to setup Hybrid configuration between your Exchange On-premises and Exchange Online.

After I had one issue like this I did some research and used Fiddler/Wireshark to check for traffic I noticed that Exchange was not encrypting traffic and testing the Migration Server Availability was reporting that the MRS service was not listening on the supposed port which is 443.

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In this case the solution was pretty easy, but still you’ll have to make a hard choice of choosing to place Exchange behind a load balancing with SSL Offloading on or not.

In my case I had to turn off the SSL Offloading on the Load balancer and that alone was enough to get this working.

Resolution:

Make sure that SSL Offloading is disabled on OWA/OA and Load balancer if there’s one.

Other resolutions:

https://support.microsoft.com/en-us/kb/3065754