How to configure max email size limit in Office 365

by Leave a comment

Sending large files or attachments can be a challenge, as Office 365 has default limits on the size of emails that can be sent and received. In this blog post, we will explore how to configure the max email size limit in Office 365, giving you greater flexibility and control over your email communications.

You may need to send large reports, presentations, or media files, this guide will help you configure the max email size restriction settings. You can set the Max email size for send and Max email size for Receive using Exchange admin center or by using Powershell.

Before we go ahead and start with the steps, you should know the defaults which are configured in Microsoft 365/Office 365 for all the users. The Default Sent messages maximum size is 35 MB (35840 KB) and Default Received messages maximum size is 36 MB (36864 KB).

For most organizations and users default email size restrictions works fine and there is no need to increase or decrease these values. However, In certain cases, you may have a large report to send or receive from a client or from an automated script. Then you can plan to change these values as per your requirement.

The Maximum Size for sent and received messages could be set to 150 MB (153600 KB). If you set it more than this value then you will receive an NDR. Also, please note that setting a higher value for sent and receive email does not gurantee the email delivery. It also depends upon the destination server sent and received email message size restrictions.

For example: If you have increased the value of Max sent email message to 150 MB and sent an email to an External email address, the email size is lets say 50 MB. The email may go out of Office 365 but if the destination server does not accept the large emails or has email message size restrictions in place, your email is most likely to be rejected.

While increasing the max email size limit in Office 365 can provide greater flexibility in sending and receiving larger files, there are some potential drawbacks to consider before making the change:

  1. Storage limitations: By allowing larger email attachments, you may be using up more storage space on your email server, which can lead to increased storage costs. Default Exchange Online Mailbox size is 100 GB.
  2. Network congestion: Sending large email attachments can also cause network congestion and slow down your email system, which can affect overall productivity.
  3. Compatibility issues: Some email systems may not be able to handle larger attachments, which can cause compatibility issues when sending or receiving emails from those systems.
  4. Security risks: Larger email attachments can also pose a security risk if they contain sensitive or confidential information. Increasing the max email size limit may make it easier for hackers to infiltrate your system or for employees to accidentally send confidential information outside of your organization.

Update Sent and Received Emails Max Size limit

You can use Exchange admin center to set Max sent and receive email size limit. You can either perform the change per mailbox or you can also select all users at once and change these values. Let’s check both the ways.

Update Sent and Received Emails Max Size limit per mailbox

  • Login on Microsoft Exchange admin center using administrator rights.
  • Click on Recipients > Mailboxes > Select any User Mailbox.
  • Click on Mailflow setting > Message size restrictions.
  • Alternatively you could also Click on the Mailbox to open User Mailbox properties pane and Go to Mailbox tab and then click on Manage message size restriction.
Message size restriction option in Exchange Admin Center for a user mailbox
  • Change the values for Sent messages maximum size(KB) and Received messages maximum size(KB) and provide new values in KB. For example to Increase the sent and received email size to 50 MB, I have set it to 51200 KB.
Manage message size restriction per mailbox

Update Sent and Received Emails Max Size limit for all users

You can easily update the Sent messages maximum size(KB) and Received messages maximum size(KB) values for all users at once instead of selecting each user and updating it. For this you would have to select all the users using Select All checkbox and then update message size restriction values. Let’s check how to perform this change:

  • Click on Recipients > Mailboxes and Click on the top checkbox next to Display name to select all the mailboxes.
  • Click on Mailflow setting > Message Size restriction.
Update Sent and Received Emails Max Size limit for all users
  • As you can see from the Message size restriction settings Pane. This shows “Apply these changes to the 18 selected recipients” which means the Sent and Received message size you will set is going to apply to all 18 selected users at once. Configure the new value here, For example: To set Sent and received email max size to 50 MB for all users, Set it to 51200 which is a value in KB.
Update Sent and Received Emails Max Size limit for all users

Update Sent and Received Emails Max Size limit for new users

Now you know how to set sent and received emails max size limit per user mailbox and also for all users at once. But what about new users which will join the organization and their new mailbox will be created. Will they get the 50 MB limit ? or the Default 35 MB limit applied ?

The default limit of 35 MB will be applied as the new mailboxes will Inherit from Organization / tenant level default Max sent and receive message limit restrictions. If you want to set message size limit values for new users then you will need to update the default settings for this. Let’s check how to perform this change:

  • Click on Recipients > Mailboxes.
  • Click on Mailflow setting > Message size restriction.
Update Sent and Received Emails Max Size limit for new users
  • On the Default message size restriction page. You can change the values of Sent messages maximum size(KB) and Received messages maximum size(KB).
  • For example: To set a default sent and received message maximum size to 50 MB for any new user mailbox, you can set the values to 51200 KB. Click Save. Now, any new mailbox created will get sent and receive message limit restriction automatically set to 50MB.
update default sent and received message maximum size restrictions

Update Sent and Received Emails Max Size limit using Powershell

If you prefer command line to update sent and received emails max size limit then you can use Powershell cmdlets as well. First you would need to Install Exchange Online Powershell module and then connect to Exchange Online using administrator rights.

Install Exchange Online Powershell Module

Install-module -Name ExchangeOnlineManagement

Connect to Exchange Online

Connect-ExchangeOnline

Example: Check Max sent and receive email size limit for AlexW@techpress.net

Get-Mailbox -Identity AlexW@techpress.net | ft MaxSendSize, MaxReceiveSize
Check Max sent and receive email size limit using powershell

Example: Set / Update Max sent and receive email size limit for AlexW@techpress.net to 150MB

Set-Mailbox -Identity AlexW@techpress.net -MaxSendSize 150MB -MaxReceiveSize 150MB
Set / Update Max sent and receive email size limit using powershell

Example: Set Max sent and receive email size limit for All users to 150 MB

Get-Mailbox -Resultsize Unlimited | Set-Mailbox -MaxReceiveSize 150MB -MaxSendSize 150MB

Set Max sent and receive email size limit for all new users using Powershell

First we need to check the default mailbox plan and then update the default mailbox plan properties for message size restrictions. Let’s check how to perform this change:

Get-MailboxPlan

Get-MailboxPlan | ft name,isdefault
Get-Mailboxplan default

Set-MailboxPlan

Set-MailboxPlan ExchangeOnlineEnterprise-3ebbec61-68ac-44d2-a506-d5577b7ec55a -MaxSendSize 150MB -MaxReceiveSize 150MB
get-MailboxPlan ExchangeOnlineEnterprise-3ebbec61-68ac-44d2-a506-d5577b7ec55a | ft name, maxsendsize, maxreceivesize
Set-MailboxPlan to increase max send and receive email size

Error If breaching the message size limit restrictions

You may get NDR (Non Delivery Report) email when you couldn’t send or receive a large email. Below email was genearted by the system when someone tried to send an email to me which was 46MB in size.

Your message wasn’t delivered to anyone because it’s too large. The limit is 35 MB. Your message is 36 MB.
Jatin Makhija (jatin.makhija@techpress.net)
 Your message couldn’t be sent because it’s too large.
Diagnostic information for administrators:
Generating server: XXXX.GBRP123.PROD.OUTLOOK.COM
jatin.makhija@techpress.net
Remote server returned ‘550 5.2.11 RESOLVER.RST.SendSizeLimit.Sender; message size (35884 KB) too large for this sender with limit 35840 KB’
Original message headers:
<<message header information>>>

Conclusion

By following the steps outlined in this blog post, you can set appropriate limits for your organization’s email attachments, preventing unnecessary delays and rejections on the emails.

If you are increasing the size limits and sending an email Internally which should be fine and there would be less rejected emails. But, if you are sending a large email to another organization, Please note that it may or may not be received by the third party email server as they may have set their email message size restrictions as per their requirement.

Leave a Comment