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Set Maximum Message Size – Setting for Existing Mailboxes

Introduction

By default, Exchange Online has a send and receive limit of 35 MB for messages, this can be increased to 150 MB.
The message size includes both the message body and attachments.

We recommend you increase the maximum message size for sent and received messages to 150 MB.

This setting should be set in conjunction with Set Maximum Message Size – Default Setting for New Mailboxes

NOTE: Setting the message size for Group Mailboxes is not support by Microsoft.

License Requirement

Any Exchange Online plan

User Impact

Low
Any existing mailboxes (except Group Mailboxes), will have a maximum message send and receive size set to the parameter in MSPMagic.

*This setting cannot apply to Group Mailboxes as Microsoft Exchange Online does not support this. MSPMagic will also ignore the Discovery Mailbox in all tenants.

Admin Portal Reference

  1. Login to the Exchange Online Admin Center as a global admin, navigate to Recipients > Mailboxes.
  2. In the list of user mailboxes, click the mailbox that you want to change the message size limits for, and then click Edit Edit icon.
  3. On the mailbox properties page, click Mailbox Features.
  4. Under Message Size Restrictions, click View details to view and change the following message size limits:
    • Sent messages: To set a maximum size for messages sent by this user, select the Maximum message size (KB) check box and type a value in the box. The message size must be between 0 and 2,097,151 KB. If the user sends a message larger than the specified size, the message will be returned to the user with a descriptive error message.
    • Received messages: To set a maximum size for messages received by this user, select the Maximum message size (KB) check box and type a value in the box. The message size must be between 0 and 2,097,151 KB. If the user receives a message larger than the specified size, the message will be returned to the sender with a descriptive error message.
  5. Click OK, and then click Save to save your changes.

PowerShell Reference

MSPMagic modifies this setting via PowerShell. The following cmdlet is run on the tenant’s Exchange Online.

Set-Mailbox -Identity <Mailbox> -MaxSendSize <$MaxSendSize> -MaxReceiveSize <$MaxReceiveSize>

If Action is set to Notify

We report the setting is compliant if all the targeted mailboxes MaxSendSize and MaxRecieveSize match the parameters set in MSPMagic.

We report the setting is non-compliant if any of the targeted mailboxes MaxSendSize and MaxRecieveSize do not match the parameters set in MSPMagic.

If Action is set to Enforce

We report the setting is compliant if all the targeted mailboxes MaxSendSize and MaxRecieveSize match the parameters set in MSPMagic.

We report the setting is compliant-fixed if MSPMagic has changed any of the targeted mailboxes MaxSendSize and MaxRecieveSize to match the parameters set in MSPMagic.

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