How to Increase Office 365 Mailbox Size to 100 GB?

  Rollins Duke
Rollins Duke   
Published: June 18th, 2025 • 8 Min Read

You ran out your Office 365 mailbox storage? And you want to extend the storage space. Then, we will help you. In this guide we are going to share with you several proven methods that can increase Office 365 mailbox size to 100 GB. But before that, you should know about the structure of Microsoft 365 mailbox.

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. To help the businesses or users in their work, there are different plans of Microsoft 365 with different prices, features and mailbox storage.
default mailbox storage in office 365

Above is the different mailbox storage of your Office 365 in different plans. With the help of this you know the default size of your mailbox. This way you can manage your storage.

When Office 365 Mailbox 50 GB Limit is Reached?

What happens when your Office 365 mailbox quota space is full or near to full. You will start receiving several or alerts. That we have mentioned below.

  • 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 prohibit sending alert messages 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: To encourage users to manage their mailbox size, some organizations implement policy. The policy restricts the mailbox access to user’s when the mailbox reaches its limits. The restrictions will remain until someone free up the space.
  • Lost Emails: If you didn’t take any actions against a full mailbox. Then you will not receive any new emails. So, you are risking missing important information. That’s why managing your mailbox is important.

Any of those warnings means that your mailbox is at a limit of exceeding. If you can’t manage the storage, you have to face several issues. This is why most organizations need to increase Office 365 mailbox size to 100 GB.

How to Check Current Office 365 Mailbox Usage?

Before you further increase your mailbox size, you have to first know the storage usage of your current Microsoft 365. In the program, you can create your report to see your mailbox usage. Follow the steps.

  1. First log in to your Microsoft 365 admin center. Click on the Reports option.
  2. Select the Usage option. It will lead to the Microsoft Usage page.
  3. Click on the View More option on the Email activity section.
  4. Choose the Exchange option and then Mailbox usage to get the report.

Once you know the size of your mailbox, follow the methods below to increase Office 365 mailbox size to 100 GB.

Upgrade Subscription to Increase Microsoft 365 Mailbox Size

If you have the budget, then upgrade your Office 365 business plan to E3 or E5. This way you will not only increase your mailbox, but also get advanced features. Below are the steps to how you do it.

  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

By upgrading to other plans, you don’t have to move your data. Your data and the settings will automatically adjust. If you don’t have money, then, use this next method.

Enable In-Place Archive to Expand Office 365 Mailbox Size

By enabling in-place archive in Office 365 you can archive old Office 365 emails to in-place archive storage. Which helps you to reduce your mailbox storage to store more data.

  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

Use Auto-Expand Archive Option to Increase Storage Space

If you use Exchange Online plan 2, Microsoft E3 or E5. then, you have the option to enable auto-expand archive which allows you to archive your mailbox automatically. When your mailbox is getting full and you have enabled this option. Your archive space will be expanded and you will be able to store more emails or data.

  1. In your Microsoft 365 Compliance Center. Go to the Data lifecycle.
  2. Select the Archive option and then click on the Enable archive button.
  3. To auto-expand the archive, open your Exchange Online PowerShell.
  4. Connect to your Exchange: Connect-ExchangeOnline -UserPrincipalName [email protected]
  5. After that, run this command for auto-expand archive: Set-Mailbox [email protected] -AutoExpandingArchive $true

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. 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 $UserCredential.
  2. Run this PowerShell cmdlet command to continue: Set-Mailbox <UserID> -ProhibitSendQuota <Value> -ProhibitSendReceiveQuota <Value> -IssueWarningQuota <Value>.
  3. Set the Mailbox Size Limit: Once connected, use the following command to set the mailbox size limit to 100 GB:
    Set-Mailbox [email protected] -ProhibitSendQuota 100GB -ProhibitSendReceiveQuota 100GB -IssueWarningQuota 98GB.
  4. Save changes and disconnect from Exchange Online, running the following command: Disconnect-ExchangeOnline -Confirm:$false.
Note That: The process to increase Office 365 mailbox size to 100 GB via PowerShell requires a Microsoft 365 administrator account to perform.

After following the above methods, you still can’t increase Office 365 mailbox size to 100 GB. try the professional method.

Increase Microsoft 365 Mailbox using Professional Software

The tool we are suggesting you is not directly used to expand your mailbox size. But, when it comes to having your storage space full. It will benefit you very much. BitRecover Office 365 Backup Tool is an expert recommended software to store your important emails, contacts, calendars and other data to your local computer. With this, your mailbox size will reduce and you can save your new emails.

The software comes with several saving options such as PST, MSG, EML, MBOX, etc. which allow you to easily access and store it. This is a brilliant way to manage your mailbox, as you can move your data from one account to another while maintaining data integrity, folder hierarchy and other attributes. Below are the working steps of the software.

Procedure to Reduce your Office 365 Mailbox Storage

  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

So, these are the ways to increase Office 365 mailbox size to 100 GB. carefully follow them so that there would be no mistakes. Especially for non-technical users.

Frequently Asked Questions

Q. How can I increase the size of mail in Office 365?
Ans. In your Exchange Admin Center, click on the Mail flow option. Select the Rules and create a new rule to allow large email sizes. Alternatively, you can use this command on PowerShell: Set-TransportConfig -MaxSendSize 100 MB -MaxReceiveSize 100 MB.

Q. How to increase the size of a shared Mailbox to 100 GB?
Ans. To increase the size of your shared mailbox to 100 GB. You have to assign an Exchange Online Plan 2 license to the shared mailbox. You can also assign any suitable Microsoft 365 subscription that provides 100 GB.

Q. Which of the 365 plans has a 100 GB mailbox?
Ans. Microsoft 365 Enterprise E3, E5, and Exchange Online Plan 2 provided a 100 GB mailbox.

Conclusion

Above we have explained different methods to increase Office 365 mailbox size to 100 GB. You can go with any method according to your preferences. We have also provided the steps to see your mailbox usage before increasing it. Each method is explained with proper steps so that anyone can easily do it. But, if you are having any problem you can contact our support team.