What are the Exchange Online Size Limits? Mailbox, Message, Attachment & More

Exchange Online Mailbox Size Limits (Based on License Type)

For instance, if you have opted for Exchange Online Plan 1, you will get a 50 GB limit for both primary and archive mailboxes. On the other hand, the default size limit for Exchange Online Plan 2 is 100 GB for the primary mailbox and 1.5 TB (auto-expanding) for the archive mailbox.

To compare license plan size limits, check out the tidy table below to know the primary mailbox size quotas and the Exchange Online archive size limit.

In line with the above, when you’re about to hit the mailbox size limit, you will receive a system-generated email with either “Your mailbox is almost full” or “Quota Exceeded” as the warning.

You will receive soft warnings, usually when you hit 98% of the quota. And if you push past 99%, Exchange Online limits you from sending new emails. Outlook or Outlook on the web will reflect this error message:

Lastly, if you are not able to send or receive new emails, it means the maximum Exchange Online size limit has been hit. All your mailbox activity will stop. And if anyone tries to send you an email, it will display a Non-Delivery Report to them: a message with a code like 5.2.2 and the message:

Exchange Online Message and Attachment Size Limit

The Exchange Online default message size limit (with attachments) is 35 MB. However, it can be expanded up to 150 MB with the admin’s manual configuration. At the same time, the number of attachments allowed per email is 250.

Microsoft imposes a strict size limit on all inbound and outbound messages. So, if you’re wondering “Why can’t I send emails?” or “Why did my email bounce?”, you have probably hit the maximum Exchange Online message size limit (email body + attachments).

How to increase the Exchange Online message size limit to 150 MB?

By using the Exchange Online PowerShell module, you can upgrade the default Exchange Online message size limit from 35 MB to the maximum limit of 150 MB.

But can you make changes to individual mailboxes? Indeed, you can, but those changes do not apply to future users. Therefore, you are required to update your existing mailboxes and your tenant’s mailbox plans. This will make sure that new accounts will automatically get the Exchange Online message size limit of 150 MB.

Steps to increase the Exchange Online Message Limit to 150 MB:

Step 1: Preparation

• In the search bar on the taskbar >> type & open Windows PowerShell as an administrator.
• Type & run the given command to install the required module:

Install-Module -Name ExchangeOnlineManagement -Force

• Again, type & run the following command to secure a connection to your tenant (use an account with Exchange Administrator or Global Administrator access):

Connect-ExchangeOnline

Step 2: Execution

• Type the command below in PowerShell to test it out on a single user account. Replace [email protected] with the email address.

Set-Mailbox -Identity "[email protected]" -MaxSendSize 150MB -MaxReceiveSize 150MB

• Now, run the given command to apply the 150 MB size limit to every active mailbox. This command will align both your regular user mailboxes and shared mailboxes.

Get-Mailbox -ResultSize Unlimited -RecipientTypeDetails UserMailbox,SharedMailbox | Set-Mailbox -MaxSendSize 150MB -MaxReceiveSize 150MB

• Next, to automatically set 150 MB as the default for newly created mailboxes, copy-paste the command below:

Get-MailboxPlan | Set-MailboxPlan -MaxSendSize 150MB -MaxReceiveSize 150MB

Step 3: Verification

To verify the changes, simply run this quick verification command:

• For a specific user:

Get-Mailbox -Identity "[email protected]" | Select-Object DisplayName, MaxSendSize, MaxReceiveSize

• For the default mailbox plans:

Get-MailboxPlan | Select-Object DisplayName, MaxSendSize, MaxReceiveSize

Exchange Online Sending and Receiving Rate Limits

Did you know that you can only send 30 messages per minute and can receive up to 3,600 messages per hour? Yes, to control spam and safeguard infrastructure, Microsoft set certain Exchange Online sending limits.

Exchange Online Hidden Limits (Most Users Don’t Notice)

Exchange Online size limits don’t stop at message sizes and storage quotas. Most users don’t know that the Exchange Online issues they’re experiencing are because of a hidden limit. So, let’s uncover them one by one!

The Recoverable Items Folder Limit

The Recoverable Items folder is a hidden data recovery destination with a default 30 GB limit. When you permanently delete an email (Shift+Delete), it moves the email to the hidden folder called the Recoverable Items folder.

So, if your Recoverable Items folder is blocked or has hit the limit, your mailbox will freeze. And worse, it won’t allow you to delete items or accept new calendar invites, ending up in an immediate IT ticket. Also, you can expand the default size limit of this hidden folder to 100 GB with litigation hold.

Auto-Expanding Archive

In the table cited above, you may have noticed that Enterprise licenses like E3/E5 offer an auto-expanding archive of up to 1.5 TB. Indeed, it is true, but it is a delayed truth.

In simple words, this archive mailbox expansion is not immediate. It means that when your archive folder reaches the full mark, Microsoft does provide extra storage, but at 1 GB per day! So, if you’re planning an immense PST migration and transferring 50 GB of old emails into a user’s archive, it will surely fail silently, because the archive can’t expand this quickly to ingest the data.

The Folder Item Limit

Exchange Online allows you to store up to 1 million items per folder (like the inbox). It does keep a record of individual items. But the catch is that Microsoft clearly states that exceeding 100,000 items in a single folder can result in the following issues:

• Performance drop
• Outlook sync issues
• Search failures (desktop Outlook client)

Author’s Take

Microsoft Exchange Online size limits differ from license to license. Therefore, it becomes very important to know the key size limits to prevent IT support tickets and manage the Exchange Online environment better.

In that pursuit, this well-researched and intuitive SysTools guide will help you navigate. It promises to help you manage the Exchange Online size limit effortlessly.

In a nutshell, practice the simple steps mentioned in this write-up and get the precise answers to the following questions:

• Exchange Online attachment size limit
• Exchange Online message size limits
• Exchange Online mailbox size limit
• Exchange Online email attachment size limit

FAQs (Frequently Asked Questions)