How to Increase Mail attachment size in Office 365 Mailbox

The default mail size limit of Office 365 mailbox is 25 MB and we can increase that limit to up to 150 MB. This is required because sometime we may need to attach some files which may be of size over 25 MB. In that case we would not be able to send or receive emails. So to deal with this situation we can increase overall message size limit of Office 365 mailbox. In this guide we will learn how to Increase Mail Size in Office 365 Mailbox so that we can even upload large size attachments. Just follow the below mentioned steps:

Video Guide to Increase or Restrict Mail Attachment in Office 365

Step 1: Login to Office 365 account and Click on Admin >> Exchange

Step 2: Click on Recipients >> mailbox >> select the mailbox and click on 3 dots >> select Set default message size restriction

Step 3: Now you can enter the maximum size of sent as well as received message.


Set the Office 365 Mailbox Limit using PowerShell Commands:

Step 1: Open PowerShell and Login to Office 365 by using the command given below:

$Login = Get-Credential

Step 2: Now enter your User Name and Password and then run the command given below:

$Session=New-PSSession –ConfigurationName Microsoft.Exchange –ConnectionUri -Credential $Login –Authentication Basic –AllowRedirection

Step 3: Run the Import -PSSession Command.

Import-PSSession $Session

Step 4: You can update the Maximum message size limit for Single as well as multiple mailboxes. Follow the commands given below to do the same.

Update Message Size Limit for Single Mailbox:

Set-Mailbox –Identity [email protected] –MaxSendSize 80MB – MaxReceiveSize 80MB

Increase Mail Attachment Size for Multiple Mailbox:

(“Mailbox1”,”Mailbox2”,”Mailbox3”)|%{Set-Mailbox –Identity $_-MaxSendSize 80MB-MaxReceiveSize 80}

Update Message Size Limit for all Mailboxes of Office 365:

Get-Mailbox | Set-Mailbox –MaxSendSize 80 MB –MaxReceiveSize 80 MB

We can also use this method to restrict the mail size limit for some users of our office 365 account.


In this article we have seen two methods to restrict or increase the message size limit in Office 365 environment. I am hoping that the information provided in this article will be helpful for you. Please share your valuable feedback regarding this article.

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