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 Read more [...]