Microsoft Exchange: Increase Maximum Message Size to 100 MB

Sometimes, the default maximum message size (including attachments) in Exchange is not enough (30 MB is the standard). To increase this to 100 MB, do the following:

First check the current maximum size on all relevant Exchange components:

Get-TransportConfig | ft MaxSendSize, MaxReceiveSize
Get-ReceiveConnector | ft Name, MaxmessageSize
Get-SendConnector | ft Name, MaxMessageSize
Get-Mailbox Administrator |ft Name, MaxsendSize, MaxReceiveSize

Then set it to 100 MB for all components:

Set-TransportConfig -MaxSendSize 100MB -MaxReceiveSize 100MB
Get-ReceiveConnector | Set-ReceiveConnector -MaxMessageSize 100MB
Get-SendConnector | Set-SendConnector -MaxMessageSize 100MB
Get-Mailbox | Set-Mailbox -MaxSendSize 100MB -MaxReceiveSize 100MB

That's it. Be aware that attachments are encoded before they are sent. This encoding adds about 30% of the size. So in reality, with the 100MB setting you can send and receive attachments that are 60 to 70 MB in size.

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