How to Increase Office 365 Mailbox Size to 100 GB?

Rollins Duke   
Published: May 6th, 2024 • 7 Min Read

This informative guide explains 5 ways to increase Office 365 mailbox size to 100 GB. Nowadays most home and business professionals use Microsoft Office 365 to do multiple tasks. Microsoft 365’s Outlook is the most famous cloud-based email application for sending and receiving emails, scheduling business and individual meetings, and organizing event information in calendars.

As we know, Microsoft 365 (Formerly Office 365) is a subscription-based business suite program that comes with multiple productivity applications such as Word, Excel, PowerPoint, OneDrive, OneNote, Planner, Teams, SharePoint, etc. Users purchase Office 365 license variants according to their work requirements. But sometimes after years of using Office 365, users see that their Office 365 quota space is nearly full. Thereafter, users start searching to increase Office 365 mailbox size over 100 GB.

Office 365 Mailbox Storage Limit

Microsoft provides different storage limits in Exchange Online that depend on your subscription plan. However, the standard mailbox size in Office 365 (Basic, Standard, Premium) is 50 GB for each user’s mailbox. However, users get 100 GB mailbox quota storage with Office 365 Enterprise licenses.

Microsoft 365 also provides 50 GB of storage space to archive emails with basic starting plans. While Office 365 premium and enterprise users get 1.5 TB of archive storage space with each license. But sometimes users still want to increase Microsoft 365 mailbox size to migrate mailbox over 100 GB to Office 365.

What Happens When Office 365 Mailbox Quota Limit Is Near to Reach?

When your Office 365 mailbox quota space is near to full then you will start receiving capacity alerts. If you are using a 50 GB standard plan then after filling in 49 GB data, users receive quota limit alerts and warnings. If you use have 100 GB enterprise subscription plan, then the alert receiving limit is 98 GB. Microsoft 365 users receive these alerts:

  • Warning Alert: Office 365 users receive a warning message when the mailbox is near its maximum size. The motive for sending this alert message is to encourage users to permanently delete unwanted Office 365 emails to receive new emails.
  • Prohibit Send Alert: Microsoft 365 users receive prohibit send alert message while the Office 365 mailbox size limit is reached to maximum size. After receiving this warning, you can’t send new emails until you clean up Office 365 mailboxes below the maximum size limit.
  • Prohibit Send/ Receive Alert: Exchange Online declines to receive any incoming email while the mailbox limit is exceeded and sends a non-delivery report (NDR) to the sender. Thereafter the sender has an option to resent the same email again. However, this is mandatory to free up some storage space by users before receiving new incoming emails.
  • Restricted Access: Some organizations implement a policy where once a mailbox reaches its limit. The user’s access to the mailbox is restricted until they free up space. This encourages users to manage their mailbox size more actively.
  • Lost Emails: If no actions are taken to free up space, then new emails that are sent to the user might get rejected or lost. There’s a risk of potentially important information being missed, and, in this case, this is difficult to restore Office 365 mailbox.

How to Check Office 365 Mailbox Storage Size?

You need to follow the steps below to check the Office 365 mailbox size. If this is nearly full then you can increase Office 365 mailbox size to 100 GB in the next upcoming section:

  1. Login to your Microsoft 365 account and choose Outlook from Apps.
    Select Outlook 365
  2. Click on the Gear icon which is also known as Settings.
    Use settings
  3. Choose the General << Storage option as shown in the figure below.
    Select storage option
  4. Now see the available and used storage space of Outlook 365 mailbox.
    See storage space

#1 Method: Increase Office 365 Mailbox Size to 100 GB via PowerShell

You can use PowerShell to increase Office 365 mailbox size over 100 GB by following these simple steps:

1 Step: Connect to Exchange Online PowerShell: Open PowerShell on your computer and run it as an administrator. Then, use the following commands to connect to Exchange Online:

$UserCredential = Get-Credential

Connect-ExchangeOnline -UserPrincipalName <[email protected]> -ShowProgress $true -UserCredential $UserCredential

2 Step: Run this PowerShell cmdlet command to continue.

Set-Mailbox <UserID> -ProhibitSendQuota <Value> -ProhibitSendReceiveQuota <Value> -IssueWarningQuota <Value>

3 Steps: Set the Mailbox Size Limit: Once connected, use the following command to set the mailbox size limit to 100 GB:

Set-Mailbox [email protected] -ProhibitSendQuota 100GB -ProhibitSendReceiveQuota 100GB -IssueWarningQuota 98GB.

4 Step: Save changes and disconnect from Exchange Online, running the following command.

Disconnect-ExchangeOnline -Confirm:$false

Note That: The process to increase Office 365 mailbox size to 100 GB via PowerShell requires a Microsoft 365 administrator account to perform. Even this facility is not available with Microsoft 365 Government, Microsoft 365 operated by 21Vianet, or Microsoft 365 Germany.

#2 Method: Upgrade Subscription to Increase Microsoft 365 Mailbox Size

As technical users know, Microsoft 365 Business Basic, Business Standard, Business Premium, and Enterprise E1 subscription plans come with 50 GB of user’s mailbox storage. But Microsoft 365 Enterprise E3 and Enterprise E5 plans are available with 100 GB quota space. Hence, you can upgrade the subscription plan to expand Office 365 mailbox size up to 100 GB. Just follow these steps to increase Office 365 mailbox size over 100 GB:

  1. Go to Microsoft 365 Admin Center.
  2. Choose the Billing option from the admin center.
    Choose billing
  3. Thereafter, select Purchase Services << Microsoft 365 as you can see.
    Expand Office 365 mailbox size
  4. Choose the Microsoft 365 Enterprise plan and click on Details.
    Microsoft 365 enterprise
  5. Select the license quantity, click the Buy button, and complete the transaction.
    Upgrade subscription increase Microsoft 365 mailbox size

#3 Method: Enable In-Place Archive to Expand Office 365 Mailbox Size

Enable in place archive in Office 365 which provides an extra 50 GB space with every Office 365 user account. Using this option users can archive old Office 365 emails to in-place archive storage. Thereafter, they can send and receive new Office 365 emails.

  1. Go to the Exchange Admin Center.
  2. Choose the Recipients option from EAC.
    Select recipients
  3. Select Mailboxes from drop-down.
    Select mailboxes
  4. Choose a user to enable an in-place archive.
    choose a user
  5. Click Username to get more details and select Others.
    Expand Office 365 mailbox size
  6. Scroll down and choose the Manage Mailbox Archive option.
    microsoft 365 increase mailbox size over 100gb
  7. Enable the mailbox archive, enter the archive folder name, and press Save to finish.
    Enable archive to increase Office 365 mailbox size over 100gb

#4 Method: Use Software to Increase O365 Mailbox Size to 100 GB

Best Office 365 Backup Tool is available for Windows and Mac OS users and allows them to export Office 365 mailbox to PST, MSG, EML, MBOX, PDF, DOC, etc. So, you can use this software to download old Office 365 emails locally and store them for future use. This software is helpful in increasing Office 365 mailbox size to 100 GB as it can download old emails by date filter. Later, you can delete old emails to expand Office 365 mailbox size limit.

  1. Launch the software, enter Office 365 credentials, and press the Login button.
    Start software
  2. Choose the required Office 365 mailbox items from the software GUI.
    Select required Office 365 folders
  3. Select a saving option according to your requirements.
    Choose PST as saving option
  4. Use the date filter to backup old emails on the local computer.
    advance filters
  5. Click Backup to start downloading emails.
    Increase O365 mailbox size to 100gb

#5 Method: Fix Clutter from Office 365 Emails

All-In-One Email Duplicate Remover Software is helpful in fixing duplicate clutter to increase Microsoft 365 mailbox size. This software has a separate option to remove duplicate emails from Office 365 mailbox so it can be more suitable for you.


Above we have explained completely detailed information to increase Office 365 mailbox size to 100 GB using multiple techniques. You can go with any method according to your preferences. We have also suggested steps to check Office 365 used and available quota space. Just use any technique with expert guidelines to increase Office 365 mailbox size over 100 GB.