unable to receive more than 35 MB from outside organization in exchange server in hybrid environment

Hi @zohaib yousuf,

Welcome to the Microsoft Q&A platform!

It looks like you have set appropriate limits for receiving emails (45 MB), but it seems there may be other limitations that need to be checked. Here are some steps to help you troubleshoot further:

1. Global Settings in Exchange Online:

   - Ensure that your Exchange Online settings align with your on-premises settings. The maximum message size in Exchange Online could be affecting your hybrid setup.

   - Use the following commands in Exchange Online PowerShell to check and modify the size limits:

     Get-TransportConfig | Format-List MaxReceiveSize,MaxSendSize

     Adjust if necessary:

     Set-TransportConfig -MaxReceiveSize 45MB -MaxSendSize 35MB

2. Connector Settings between Exchange Online and On-premises:

   - The connectors that facilitate mail flow between Exchange Online and your on-premises Exchange might have their own size limitations.

   - To check the connector settings in Exchange Online PowerShell:  

     Get-InboundConnector | Format-List Name,MaxMessageSize
     Get-OutboundConnector | Format-List Name,MaxMessageSize

     Adjust if necessary:

     Set-InboundConnector "Connector Name" -MaxMessageSize 45MB
     Set-OutboundConnector "Connector Name" -MaxMessageSize 35MB

3. Double-Check Receive Connector Settings:

   - Verify all receive connectors to ensure no other connectors are imposing a lower limit.

   - Run:

     Get-ReceiveConnector | Format-List Name,MaxMessageSize

   - Ensure each connector has the correct settings.

4. Ensure Proper Authentication:

   - Sometimes, emails from outside organizations might not be authenticated properly and could hit anonymous receive connector limits.

   - Verify that the external email is being processed by the correct connector that has a higher limit.

5. Account for Encoding Overhead:

   - Remember that email attachments are typically encoded (e.g., Base64), which adds approximately 33% to the size of the email. So a 30 MB attachment could result in a message size closer to 40 MB.

6. Exchange Online Protection (EOP):

   - If you have EOP in place, ensure it is not imposing additional restrictions.

   - Check the inbound and outbound connector limits within EOP.

7. Testing:

   - Conduct a test by sending a slightly smaller email (e.g., 25 MB) from an external source to ensure it is properly received.

   - Gradually increase the size to determine the exact threshold at which the issue occurs.

8. Re-run Hybrid Configuration Wizard:

   - Sometimes, re-running the Hybrid Configuration Wizard can resolve discrepancies between your on-premises and Exchange Online settings.

Please feel free to contact me if you have any queries.

Best,

Jake Zhang

Hi @zohaib yousuf,

Great to know that the issue has already been resolved and thanks for sharing the solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others", I'll repost your solution in case you'd like to "Accept" the answer : )     

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Issue Symptom: 

Unable to receive more than 35 MB from outside organization in exchange server in hybrid environment.

Resolution: 

This issue can be resolved by set organization limit.

Best,

Jake Zhang