Message Size/Attachment Size Limit in Office365

Change Office 365/Exchange Online/Microsoft 365 Message Limit

1. Log in to the Exchange Online Admin Center:

- Open a web browser and go to the URL of the Exchange Online Admin Center. https://admin.exchange.microsoft.com

- Log in with an account that has administrative privileges.

For All the Users:

- Expand Recipient > Mailboxes > Mailflow Settings > Default Message Size Restrictions

• Send Messages Maximum Size (KB) : 35840

• Received Messages Maximum Size (KB) 35840

For Specific User:

- Expand Recipient > Mailboxes > Select the mailbox that you want to change the settings > Mailbox > Mail flow Settings > Message Size Restrictions > Manage message size restrictions

• Send Messages Maximum Size (KB) : 35840

• Received Messages Maximum Size (KB) 35840

Using Exchange Online PowerShell

You can also adjust the message size limit using PowerShell commands in the Exchange Online Power Shell.

PS Command to Change Maximum Send Size for Mailbox Plan

Set-MailboxPlan -MaxSendSize 100MB -MaxReceiveSize 100MB

To Verify:

Get-MailboxPlan | ft MaxSendSize, MaxReceiveSize

This sets the maximum send message size to 100MB. You can adjust the size as required.

PS Command to Change Message Size for a Specific Mailbox

To modify the send and receive limits for a specific mailbox:

Set-Mailbox "Mailbox Name" -MaxSendSize 100MB -MaxReceiveSize 100MB

To Verify:

Get-Mailbox -Identity "Mailbox Name" | ft MaxSendSize, MaxReceiveSize

This will change both the maximum send and receive size to 100MB for that mailbox.

PS Command to Change Message Size for a All Mailboxes

Get-Mailbox | Set-Mailbox -MaxSendSize 100MB -MaxReceiveSize 100MB

That’s it! By following these steps, you should be able to change the message size limits for your Office 365 Tenant as needed.