Throttling policy is a feature in Microsoft Exchange 2013 which provides flexibility to restrict messages and device connections to Exchange Server. In this article, we will explain gradually how we can allow or restrict a mailbox to configure only on one mobile device while the default limit is 10.

By default, each mailbox has a Global Throttling Policy. It is not recommended to change that policy -- instead, create a new throttling policy and assign it to the mailbox.

Objective

Our objective in this article is to restrict the "IT.infra" mailbox to allow ActiveSync Exchange configuration only on one mobile device while by default a mailbox can be configured on 10 devices.

Step-by-Step Configuration

Step 1: Create a New Throttling Policy

Create a new Throttling Policy with the name "1Mobile":

New-ThrottlingPolicy -Name "1Mobile" -ThrottlingPolicyScope Regular

Step 2: Verify the New Policy

The following command will show the new policy and limits which are inherited from the Global policy:

Get-ThrottlingPolicy -Identity "1Mobile" | select *Eas*

Step 3: Set Device Limits

This command will set the concurrent connection to 1 and the allowed mobile device count to 1:

Set-ThrottlingPolicy -EASMaxDevices 1 -EASMaxConcurrency 1 -Identity "1Mobile"

Step 4: Verify the New Values

The following command will show the new values set using the above command:

Get-ThrottlingPolicy -Identity "1Mobile" | select *Eas*

Step 5: Assign the Policy to a Mailbox

In this step, we will assign this policy to the mailbox "IT.Infra":

Set-Mailbox "It.Infra" -ThrottlingPolicy "1Mobile"

Step 6: Verify Policy Assignment

We can verify if the policy is assigned correctly to this mailbox:

Get-Mailbox -Identity "IT.infra" | select name,*Th*

Bonus: Restrict OWA Sessions

You can also restrict OWA to keep one session by using the property -OWAMaxConcurrency 1, so a user can only open one session of OWA at a time.

Modern Alternative: Intune and Conditional Access

The throttling-policy approach above is specific to on-premises Exchange Server and controls only how many ActiveSync device partnerships a mailbox can have — it doesn't evaluate device health, encryption, or compliance. If you're managing devices in Exchange Online or a hybrid tenant, Microsoft's current guidance is to move device restrictions to Microsoft Intune device compliance policies combined with Conditional Access, rather than relying on ActiveSync device-count limits alone. This gives you per-platform rules, compliance-based (not just count-based) access decisions, and centralized reporting, and it fits Microsoft's broader Zero Trust device-management direction. The on-premises throttling policy method in this article is still valid for Exchange Server 2013/2016/2019 mailboxes where Intune/Conditional Access isn't in play.

Reference

Microsoft Docs: Set-ThrottlingPolicy

Frequently Asked Questions

What happens when a user exceeds the EASMaxDevices limit?

When a user tries to configure ActiveSync on a new device after reaching the limit, the connection will be denied. The user will need to remove an existing device partnership before adding a new one, or an administrator can increase the limit.

Can I apply different throttling policies to different users?

Yes, you can create multiple throttling policies with different limits and assign them to different mailboxes. For example, executives might be allowed 5 devices while standard users are limited to 1 or 2.

Does this affect devices that are already configured?

Existing device partnerships are not automatically removed when you apply a stricter throttling policy. However, if a user has more devices than the new limit allows, they will not be able to add new devices until they are below the limit.

How do I remove a throttling policy from a mailbox?

To remove a custom throttling policy and revert to the default Global policy, use the following command:

Set-Mailbox "IT.Infra" -ThrottlingPolicy $null

Is this method supported in Exchange Online (Office 365)?

Exchange Online uses mobile device access rules and mobile device mailbox policies instead of throttling policies. The New-ThrottlingPolicy cmdlet is only available in on-premises Exchange 2013/2016/2019. For Exchange Online and hybrid tenants, Microsoft recommends managing device access with Intune device compliance policies and Conditional Access instead — see the "Modern Alternative" section above.

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