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Attachment size limit in Exchange Server

Users can’t send an attachment in Outlook Web Access. A notification shows that the files weren’t attached because it would cause the message to exceed the maximum size limit of 10 MB. Why are users getting Exchange message size limit, and what is the solution against Exchange size limit attachments? This article will show how to change and increase the Exchange attachment size limit in Exchange Server.

Exchange attachment size limit

A user wants to send a message from Outlook Web Access (OWA). When sending the email, a message shows up:

The following files weren’t attached because adding them would cause the message to exceed the maximum size limit of 10 MB.

Attachment size limit Exchange 2016 OWA notification

This is what it looks when the user wants to send an email from the Outlook application:

This email message cannot be sent because it exceeds the 10 MB outgoing message size limit. We won’t be able to deliver this message because it’s too large.

Attachment size limit Exchange Server Outlook notification

Why do users get this notification, and what is the solution for Exchange maximum attachment size limit?

Get information attachment size limit Exchange

We will check the current Exchange message size limit in the Exchange organization. Run Exchange Management Shell as administrator. We need to run the following four commands.

1. Transport configuration

First, we will check the transport configuration max send size and max receive size. Run the Get-TransportConfig cmdlet.

[PS] C:\>Get-TransportConfig | ft MaxSendSize, MaxReceiveSize

MaxSendSize              MaxReceiveSize
-----------              --------------
10 MB (10,485,760 bytes) 10 MB (10,485,760 bytes)

2. Receive connector

The second cmdlet is to get the receive connector max message size. Run the Get-ReceiveConnector cmdlet.

[PS] C:\>Get-ReceiveConnector | ft Name, MaxmessageSize

Name                              MaxMessageSize
----                              --------------
Default EX01-2016                 36 MB (37,748,736 bytes)
Client Proxy EX01-2016            36 MB (37,748,736 bytes)
Default Frontend EX01-2016        36 MB (37,748,736 bytes)
Outbound Proxy Frontend EX01-2016 36 MB (37,748,736 bytes)
Client Frontend EX01-2016         36 MB (37,748,736 bytes)

3. Send connector

The third command that we will check is the send connector max message size. Run the Get-SendConnector cmdlet.

[PS] C:\>Get-SendConnector | ft Name, MaxMessageSize

Name            MaxMessageSize
----            --------------
Internet e-mail 35 MB (36,700,160 bytes)

4. Mailbox

The fourth and last command to check is the user mailbox max send size and max receive size. This is the mailbox of the user that sends the message. Run the Get-Mailbox cmdlet.

[PS] C:\>Get-Mailbox james.paterson@exoip.com | ft Name, MaxSendSize, MaxReceiveSize

Name           MaxSendSize MaxReceiveSize
----           ----------- --------------
James Paterson Unlimited   Unlimited

Solution Exchange attachment size limit

Now that we gathered all the information, we can see that the transport configuration maximum size is:

  • MaxSendSize 10 MB (10,485,760 bytes)
  • MaxReceiveSize 10 MB (10,485,760) bytes)

Change attachment size limit Exchange Server

Let’s change the limit for both the message sent and the message received.

We will run the Set-TransportConfig cmdlet.

[PS] C:\>Set-TransportConfig -MaxSendSize 20MB -MaxReceiveSize 20MB

Restart Exchange Server services with PowerShell

Wait for several hours before the change will take effect. If you want the change to take effect immediately, restart the Exchange Server or restart the Exchange Server services.

Note: Because the Exchange Server has a cache for various settings, this change does not take effect immediately. You may have to wait several hours before this change is recognized by Outlook/Outlook Web Access (OWA).

In our example, we will restart Exchange Server services through PowerShell.

[PS] C:\>Get-Service *Exchange* | Where {$_.DisplayName -notlike "*Hyper-V*"} | Restart-Service -Force

Verify and test uploading attachment

Run the Get-TransportConfig cmdlet to verify the changes.

[PS] C:\>Get-TransportConfig | ft MaxSendSize, MaxReceiveSize

MaxSendSize              MaxReceiveSize
-----------              --------------
20 MB (20,971,520 bytes) 20 MB (20,971,520 bytes)

Close all browsers and sign in to OWA. Then, attach the file and verify that it works.

Attachment size limit Exchange 2016 PDF uploaded

Restart the Outlook application. Next, attach the file and verify that it works.

Attachment size limit Exchange Server Outlook PDF uploaded

The users can send attachments up to 20 MB from now on. The exchange attachment size limit is successfully fixed!

Note: Sending attachments in OWA can’t be larger than 25 MB in total. So if you set a 100 MB maximum allowed send size, you could only attach a total of 25 MB in attachment size in a single message using OWA. Use the Outlook application to send attachments and overcome the 25 MB limit in OWA after you set the maximum size limit.

Read the next part if you like to change the transport config in Exchange Admin Center.

Change attachment size limit in Exchange Admin Center

Sign in to the Exchange Admin Center (EAC) with an admin privileges account. Navigate to mail flow > receive connectors. Click the More … icon in the toolbar and click Organization transport settings.

Attachment size limit Exchange 2016 receive connectors

Change Maximum receive message size (MB) and Maximum send message size (MB) to 20. Click Save.

Attachment size limit Exchange 2016 organization transport settings receive connectors

Restart the Exchange Server services

Wait for several hours before the change will take effect. If you want the change to take effect immediately, restart the Exchange Server or restart the Exchange Server services.

Note: Because the Exchange Server has a cache for various settings, this change does not take effect immediately. You may have to wait several hours before this change is recognized by Outlook/Outlook Web Access (OWA).

In our example, we will restart Exchange Server services through PowerShell.

[PS] C:\>Get-Service *Exchange* | Where {$_.DisplayName -notlike "*Hyper-V*"} | Restart-Service -Force

Another option is to open the services console and search for Microsoft Exchange. Then, restart the services one by one.

I hope that this article helped you to fix the Exchange size limit attachments.

Keep reading: Search message tracking logs in Exchange »

Conclusion

You learned how to change attachment size limit in Exchange Server. First, run the four commands in the article to check the max send size and max receive size. After that, adjust the values with Exchange Management Shell or in Exchange Admin Center. From now on, users can send attachments higher than the maximum size limit of 10 MB. You can find more information regarding this topic on Microsoft Docs.

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ALI TAJRAN

ALI TAJRAN

ALI TAJRAN is a passionate IT Architect, IT Consultant, and Microsoft Certified Trainer. He started Information Technology at a very young age, and his goal is to teach and inspire others. Read more »

This Post Has 7 Comments

  1. I just want to say thank you for this great website. I found a solution here on alitajran.com for my issue.

  2. Hi, We had a requirement to enable 40 mb as attachment. We did on global for every one. But set the exception to send only for VIP users through mail flow rules. Rest all users should be 8MB. I created the rule but normal users still can send big emails if they select multiple attachments. If they select one attachment larger that 8MB then the rule is being applied. For multiple smaller attachments even in total larger than 8MB rule is not applied.

  3. I’m pretty sure you only have to restart the transport service, not everything.

    Restart-Service MSExchangeTransport

    1. Only restarting the Microsoft Exchange Transport service will not work. I tested it on a clean Exchange Server 2016 and Exchange Server 2019. Restart all the Exchange services or restart the Exchange Server. That’s if you want the change immediately to take effect.

      You don’t have to restart the Exchange services. Note that the Exchange server has a cache for various settings. This change does not take effect immediately. You may have to wait several hours before this change is recognized.

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