PowerShell issue while trying to adjust mailbox transport settings in Exchange Server

Hi @Schott Cyndi

Thank you for posting your question in Microsoft Q&A. 

Based on Set-MailboxTransportService (ExchangePowerShell) | Microsoft Learn, looks like this cmdlet specifically configures the Mailbox Transport service on Mailbox servers, which handles internal message delivery between mailboxes and the Transport service. However, it does not include a -MaxSendSize parameter for adjusting message size limits, those are managed elsewhere in Exchange’s transport configuration. 

Additionally, configure 50GB is far beyond any practical or supported mail flow size in Exchange. Typical values are 50–100 MB, Exchange Online’s upper bound is around 150 MB (varies). Even on-premises, connectors and clients limit effective sizes .I would recommend using a value like 50 MB for message size settings, as this aligns with best practices and supported limits. 

Since your goal is to update message size limits at the server level, you could consider use the following commands: 

For Organization-wide defaults (affects all servers unless overridden) 

Set-TransportConfig -MaxSendSize 50MB -MaxReceiveSize 50MB 

This sets the global max for messages processed by the Transport service. You could use this command to check current values:

Get-TransportConfig | Format-List MaxSendSize,MaxReceiveSize

Changes might take up to 1 hour to propagate (or restart the Microsoft Exchange Transport service immediately with Restart-Service MSExchangeTransport). 

For Connectors (inbound/outbound paths): 

Receive Connectors (for incoming mail): 

Get-ReceiveConnector | Format-Table Name,MaxMessageSize  
Set-ReceiveConnector -Identity "Name" -MaxMessageSize 50MB 

Send Connectors (for outgoing mail): 

Get-SendConnector | Format-Table Name,MaxMessageSize  
Set-SendConnector -Identity "Name" -MaxMessageSize 50MB 

For Mailbox-level overrides (mailbox level reference), use: 

Set-Mailbox -Identity "******@domain.com" -MaxSendSize 50MB -MaxReceiveSize 50MB 

Or for all mailboxes: 

Get-Mailbox | Set-Mailbox -MaxSendSize 50MB -MaxReceiveSize 50MB 

References: 

Set-TransportConfig (ExchangePowerShell) | Microsoft Learn 

Message size and recipient limits in Exchange Server | Microsoft Learn 

I hope this helps. 

Please feel free to correct me if I misunderstood your request. If you have any additional concerns, feel free to comment below. I would be more than happy to assist. 

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