How to Increase Mailbox Size in Office 365

Have you reached your Office 365 mailbox size limit and want to know how to increase it? Then we first have to check if you can increase the mailbox within your current Office 365 plan.

Depending on your Microsoft Office 365 plan you can have either a 50GB or a 100GB mailbox size as you can see in the table below.

If you have reached the limit within your plan, then we still have two options. We can either move the mail to the Online Archive or in some cases switch over to a different Office 365 subscription.

Microsoft Office 365 PlanExchange
Online Plan
Mailbox sizeOnline Archive size
Microsoft 365 Business BasicPlan 150GB50GB
Microsoft 365 Business StandardPlan 150GB50GB
Microsoft 365 Business PremiumPlan 150GB50GB
Office 365 F1Kiosk2GBAdd-on
Office 365 E1Plan 150GB50GB
Office 365 E3Plan 2100GBUnlimited
Office 365 E5Plan 2100GBUnlimited
Microsoft 365 F3Kiosk2GBAdd-on
Microsoft 365 E3Plan 150GBUnlimited
Microsoft 365 E5Plan 150GBUnlimited

Microsoft has increased in the mailbox limitation in the past, in 2013 and later again for the E3 and E5 plans. So if your mailboxes were created before 2016 then it’s possible that your mailboxes still have the old limits, 25Gb instead of 50Gb for Exchange Online plan 1 and 50Gb instead of 100Gb for plan 2.

Also when you have upgraded your Office 365 plan to E3, for example, then the mailboxes may still have the old mailbox size limit.

You can check the current mailbox size of a user in the Exchange Admin Center.

increase mailbox size office 365

Or with PowerShell

# Connect to Exchange Online
Connect-Exchangeonline -userprincipalname [email protected]

# Get the mailbox size limits
Get-Mailbox -identity [email protected] | select IssueWarningQuota, ProhibitSendQuota, ProhibitSendReceiveQuota

# Get all mailbox sizes
Get-Mailbox | select DisplayName, IssueWarningQuota, ProhibitSendQuota, ProhibitSendReceiveQuota

Increase Mailbox size Office 365 with PowerShell

Increasing the mailbox size can only be done with PowerShell. You will need to have the Exchange Online Module installed before you can connect to Exchange Online with PowerShell.

We need to set 3 values:

  • IssueWarningQuota – When the warning is displayed in Outlook
  • ProhibitSendQuota Determines when the user can’t send mail anymore
  • ProhibitSendReceiveQuota The user can’t send or receive mail when reached

You want to give the user a warning on time, not when the mailbox limit is reached. So we set the warning to 95Gb. Then prohibit the sending of new mail at 98Gb, so we still have a little room to receive mail until we reach the limit of 100Gb.

# Connect to Exchange Online
connect-exchangeonline -userprincipalname [email protected]

# Increase mailbox size
Set-Mailbox -identity [email protected] -IssueWarningQuota 95GB -ProhibitSendQuota 98GB -ProhibitSendReceiveQuota 99GB

You can also increase all the mailboxes in one command. If all your users have the same licenses then you can simply run the following PowerShell command to increase mailbox size to 100Gb in Office 365.

Get-Mailbox | Set-Mailbox -identity [email protected] -IssueWarningQuota 95GB -ProhibitSendQuota 98GB -ProhibitSendReceiveQuota 99GB

If you have a large tenant with different Microsoft Office 365 plans for your users then you can’t increase all the mailboxes. You could run the command above, but it will throw a lot of errors for all the mailboxes that can’t be changed.

With the command below we get all the user mailboxes (not the shared) and select the mailboxes that have a ProhibitSendReceiveQuota of 50GB. Also, we need to make sure that the user has an Exchange Online Plan 2 mailbox, which we do with BPOS_S_Enterprise. (BPOS_S_Standard is EO Plan 1)

Get-mailbox -Filter {RecipientTypeDetails -eq "UserMailbox"} | 
Where-Object {($_.ProhibitSendReceiveQuota -eq '50 GB (53,687,091,200 bytes)') -and ($_.PersistedCapabilities -contains "BPOS_S_Enterprise")} | 
Set-mailbox -ProhibitSendQuota 98GB -ProhibitSendReceiveQuota 99GB -IssueWarningQuota 95GB

Enable Office 365 Online Archive

If you have reached the limits of your Office 365 plan then your only option is to start moving the mail older than 2 years to the Online Archive.

We first have to check if the archive is enabled in the Exchange Admin Center. If you open the mailboxes you will see a column with the Archive Status. If the Archive Status is none then we can enable it.

  1. Select the user
  2. Click on Manage mailbox archive
  3. Enable the archive.
office 365 increase mailbox size 100gb

We can also use PowerShell to enable the Office 365 Online Archive

# Connect to Exchange Online
connect-exchangeonline -userprincipalname [email protected]

# Enable the mailbox for John Doe
Get-mailbox -Identity [email protected] | Enable-Mailbox -Archive

If you want to enable the archive for all users then use the following PowerShell cmd:

# Connect to Exchange Online
connect-exchangeonline -userprincipalname [email protected]

# Enable the Online Archive for all mailboxes
Get-mailbox -Filter {ArchiveStatus -eq 'none' -and RecipientTypeDetails -eq "UserMailbox"} | Enable-Mailbox -Archive

Retention Tag Policies

We can use retention tag policies (RTP) to move the mail automatically to the archive. By default, there should be an RTP that archives all the mail older then 2 years to the archive.

In the old Exchange Admin Center, select compliance management > retention tags. There should be a “Default 2-year move to archive” policy that moves the mail to the archive after 730 days (2 years).

office 365 increase mailbox size 100gb

Retention Tags are assigned to a Retention Policy, which is again assigned to a mailbox. The default retention policy is always assigned to a mailbox if no other policy is assigned.

Frequently Asked Questions

What is the Exchange Online plan 1 mailbox size

The Exchange Online Plan 1 mailbox is 50GB and the size of the online archive is also 50Gb

What is the Exchange Online plan 2 mailbox size

The Exchange Online Plan 2 mailbox is 100GB and the size of the online archive is unlimited

What is the Exchange Online Kiosk mailbox size

Kiosk mailboxes are only 2GB and don’t come with an online archive. It’s possible to buy the online-archive as an add-on.

Can you increase the Office 365 mailbox size over 100gb

No, you will have to use the online archive for this.

Wrapping Up

Increasing the mailbox size in Office 365 only solves the problem temporarily (or for a couple of years). At the moment you can’t go beyond the 100GB for a mailbox, so make sure you have the archive mailboxes enabled and retention policies the move the mail after 2 years to the archive.

Another good way to limit the growth of the mailboxes is to train your users to share links to documents instead of attaching the document.

If you have any questions, just drop a comment below.

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3 thoughts on “How to Increase Mailbox Size in Office 365”

  1. What is the Exchange Online plan 1 mailbox size
    The Exchange Online Plan 1 mailbox is 50GB and the size of the online archive is 100Gb

    The table says otherwise. In my understanding, mailbox size + archive can be 50GB overall, not 50 + 50 as the table says.
    So… three opinions 🙂 What’s correct?

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