Somethimes, the default maximum message size (including attachments) 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.