January 2019

How to work with Inactive Mailboxes in a Hybrid Environment

Tuesday, January 29, 2019

Earlier today the Exchange team posted an article on the EHLO Blog explaining how to manage inactive mailboxes in Exchange Online. That blog post is geared mainly toward cloud-only tenants. This article gives information about the differences between inactive users and shared mailboxes and how to configure them both in a hybrid environment.

Inactive vs Shared Mailboxes

Most customers are interested in a way to remove the Office 365 license from terminated users to reduce costs, while maintaining access to their email. There are two ways to do this.

Inactive mailboxes are mailboxes that have been put on litigation hold and the Office 365 licenses have been removed from the user account in Azure AD. Normally when you remove an Exchange Online license from a user account, the mailbox becomes disconnected and will eventually be purged from EXO (30 days by default). However, if the mailbox is placed on litigation hold before the user account is deleted or unlicensed, EXO is unable to delete the mailbox until the lit hold is removed.

Shared mailboxes are mailboxes that multiple users can access to read and send e-mail messages. Shared mailboxes allow a group of users to view and send e-mail from a common mailbox. This type of mailbox also does not require an EXO license, but has some limits placed on it to prevent abuse.

I put together a table that lists some of the important differences between Inactive and Shared mailboxes that may help you chose which one to use. Neither require an EXO license.

Characteristic	Inactive Mailbox	Shared Mailbox
Requires an EXO license	No	No
Accessed by	Only by users with Discovery Management role	Any user with Full Access rights or with Discovery Management role
Can receive new emails	No	Yes
Can send new emails	No	Yes
Mailbox size limit	100 GB	50 GB
Supports online archive mailboxes	Yes	Yes, but requires a license
Messages can be changed or deleted	No	Yes

Note: There are other limits and requirements, as well. See Exchange Online Limits for the complete list.

Inactive mailboxes are just that -- inactive. The mailbox contents are in stasis and cannot be changed. No new emails can be sent or received by an inactive mailbox. The original user cannot access the mailbox because the account has been deleted or the Office 365 license(s) have been removed. Only users with the Discovery Management role can access the historical mailbox contents. If a user was granted full access to that mailbox prior to removing the license(s), the mailbox may still show in Outlook, but the contents will be inaccessible.

Some organizations chose to convert mailboxes for terminated users into shared mailboxes instead and assign full access to the user's manager or another team member or group. That way, emails sent to the shared mailbox don't bounce with an NDR and the user with full access can respond for the termed employee. Just keep in mind the size and archive limits listed above. See Correcting Shared Mailbox provisioning and sizing for more details.

How to Configure an Inactive Mailbox in a Hybrid Environment

Normally in a hybrid environment all user and mailbox management is done on-premises and the configuration changes sync to the cloud. However, configuring litigation hold for an inactive mailbox is performed directly in Exchange Online.

Follow the first two steps listed in the EHLO Blog article. These are performed in the Microsoft Exchange Online Powershell Module.

1. Put the mailbox on a hold (which will also place the Archive on the hold, if it is present). For this scenario I’ve used LitigationHold, but, any hold from Exchange Online, or Security and Compliance can be used:

Set-Mailbox David -LitigationHoldEnabled $True -LitigationHoldDuration Unlimited

Note: The hold setting may take up to 60 minutes to take effect.

2. Ensure the mailbox has Litigation Hold enabled:

Get-Mailbox David | fl PrimarySMTPAddress, Identity, LitigationHoldEnabled, LitigationHoldDuration, MailboxPlan, PersistedCapabilities, SKUAssigned

User properties should now show:

PrimarySmtpAddress : David@contoso.com

Identity : David

LitigationHoldEnabled : True

LitigationHoldDuration : Unlimited

MailboxPlan : ExchangeOnlineEnterprise-0527a260-bea3-46a3-9f4f-215fdd24f4d9

PersistedCapabilities : {BPOS_S_O365PAM, BPOS_S_ThreatIntelligenceAddOn, BPOS_S_EquivioAnalytics, BPOS_S_CustomerLockbox, BPOS_S_Analytics, BPOS_S_Enterprise}

SKUAssigned : True

3. Wait for Azure AD Connect to replicate the change back to on-premises or you can force AAD replication using the following command on your AAD Connect server:

Start-ADSyncSyncCycle -PolicyType delta

4. Now you can either delete the user's AD account from on-premises, which will sync to ADD and remove the user account there. The inactive mailbox will not be deleted because it's on indefinite litigation hold. Use the procedures here to access the inactive mailbox.

How to Configure a Shared Mailbox in a Hybrid Environment

First, it's important to know that it's recommended that you do not convert a mailbox that was migrated to Exchange Online to a shared mailbox. The mailbox should be moved back to on-prem, converted to a shared mailbox, and remigrated to Office 365 again. The reason is that AAD Connect doesn't sync the correct attributes back to on-premises. See Convert a user's mailbox in a hybrid environment for more details.

That said, it is possible to convert a migrated user mailbox to a shared mailbox by updating AD on-premises manually. Jetze Mellema blogged about it here. Just follow these steps:

1. Sign-in to the Exchange Online Admin Center and navigate to Recipients > Mailboxes.

2. Select the user account you wish to convert and select Convert to Shared Mailbox on the right-side pane. The mailbox will now show under Shared mailboxes in the Exchange Admin Center in Exchange Online.

3. In AD on premises, change the following two attributes for the user account. This can be done using ADSIEdit or the Advanced view of AD Users and Computers on the Attributes tab.

msExchRemoteRecipientType: 100
msExchRecipientTypeDetails: 34359738368

4. Remove the Office 365 licenses from the Shared mailbox.

5. Disable the user account in AD on-prem and Windows will manage its password. The mailbox will now show under Shared mailboxes in the Exchange Admin Center on premises.

Enable Outlook Automapping for Exchange mailboxes

Wednesday, January 23, 2019

When a user is delegated full access rights to another mailbox, automapping will automatically add that mailbox to that user's Outlook. Automapping does this when Outlook runs a background autodiscover process and discovers that the user has been given full access to another mailbox. The user doesn't need to add the mailbox manually to Outlook and will be unable to remove the additional mailbox.

Automapping is enabled by default, but it can be disabled by running the following cmdlet:

Add-MailboxPermission TeamMailbox -User kmeyer -AccessRights FullAccess -AutoMapping $false

The cmdlet above gives user Ken Meyer full access to the TeamMailbox mailbox and disables automapping for that mailbox.

I published the Enable-AutomappingForFullAccessMailboxes.ps1 script for Exchange in the Microsoft Script Center Gallery. The script re-enables Outlook automapping on mailboxes where users have been given full access rights. It runs on Exchange 2010-2019 and Exchange Online, and must be run from the Exchange Management Shell (EMS).

Introducing the OME Test Tool

Saturday, January 12, 2019

tldr; Send an email to OMETest@expta.com and the service will respond with an email encrypted by Office 365 Message Encryption. If your test email includes an attachment, that attachment will be included in the OME encrypted response as an encrypted attachment. Use this service to test how encrypted emails are handled by your email clients and mobile devices.

The well-intentioned folks over at Microsoft are doing it again, but you know what they say about the road to hell...

In late December message ID MC170958 showed up in the Office 365 Message Center entitled, "New Office 365 Message Encryption policy for sensitive information." This feature is intended to keep user emails that contain sensitive information safe by automatically encrypting them. This will be done by creating a new Exchange mail flow rule in your tenant to use Online Message Encryption (OME), which was recently renamed to Office 365 Message Encryption.

Message Center ID MC170958

The Message Center notice included a link to https://docs.microsoft.com/en-us/office365/securitycompliance/new-ome-encryption-policy, but that link no longer works for most users. Perhaps Microsoft is rethinking this, but it still shows in the Message Center for some customers.

While the idea of keeping users from doing something stupid is a noble one, to me this reeks of Skynet. I really don't like the idea of anyone or anything inserting logic and a new business process into my emails and mail flow. What if my emails to customers start being encrypted because my item numbers resemble a bank account number? What if I have a complex transport configuration?

It's easy enough to opt-out of this change by running Set-IRMConfiguration -AutomaticServiceUpdateEnabled $false, but shouldn't I really have to opt-in instead of opt-out?

January 25 UPDATE: Microsoft has indeed rethought this a bit. They will still be creating the OME transport rule, but it will not be enabled by default:

Updated Message Center Notification

I'm sure automation like this might help small customers who don't have the time or skills to properly manage and secure their infrastructure, but for enterprise customers this could be a real disaster. OME encrypted emails require the recipient to authenticate with a Microsoft account to read them. Despite what Microsoft thinks, not everyone has (or wants) an account with them or uses Microsoft Office. This causes a barrier that a lot of email recipients will find difficult. It should be noted that one-time passwords are also supported. Read Microsoft Plans to Launch Automatic Email Encryption for Office 365 Tenants for Tony Redmond's take on this.

I created an OME test service in Office 365 that you can use to test the end-user experience of receiving an OME encrypted email. Simply send an email to ometest@expta.com. In a short while the service will automatically respond with an encrypted message. If you include an attachment with your email, that attachment will also be returned in the OME message as an encrypted attachment.

Note: The OME test service will not respond to messages that contain ": " in the subject. This prevents mail loops caused by rules that automatically reply or forward messages.

You should test access to this encrypted email from Outlook or any desktop email app, your mobile device, and your web browser to see how each client handles OME encrypted emails. You may be required to create a free Microsoft ID to view it.

You'll notice that you cannot preview OME encrypted emails in the Outlook preview pane. They must be opened to view them.

OME encrypted emails cannot be viewed in the preview pane

Outlook will attempt to download a rights management service user license to make the reading experience fairly straightforward, assuming you're signed into Office 365. Other email clients will be more cumbersome and recipients without a Microsoft account will need to sign up for one to read the email. Honestly, I can't imagine my parents having to deal with this from their mobile phones.

This is what an OME protected email looks like on an iPhone

I use the native Apple mail client, not the Outlook app. If you're like me, you have more than one email account on your mobile device. When you click "Read the message" you'll need to authenticate with the same email address it was sent to - something that may not be readily apparent from an "All Inboxes" view, like on the iPhone. If you use the wrong account you get an unhelpful "The item was not found" error.

Once you successfully sign-in to Office 365 you can view, reply, or forward the email via OWA. If you use the Outlook app for iOS or Android, your experience will be better.