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Receive Message Sizes with connectors and Global Transport settings RRS feed

  • Question

  • Hi

    To send and receive mails with attachments of size 20 MB we did the configuration as mentioned below

    -> Modified Global Receive and Send message size to 28 MB (we have SMTP smart host & other security devices facing internet, it will add additional overhead to 20 MB mails, so mentioned 28 MB as global size ) 

    -> Modified Receive size with Default Frontend connectors of each server with 28 MB 

    -> Modified Receive size with Default Server connectors with each server with 20 MB

    Here for testing we modified Default Server connectors with each server with 16 MB, but still we are receiving mails with size 20 MB from internal and external users. How this works? Our understanding is, for incoming external mails most restrictive policy will be applied, here the most restrictive is Default Server connectors with 16 MB.

    Thanks in advance  


    LMS

    Wednesday, October 3, 2018 1:05 PM

All replies

  • We failed to get a full clarification with Receive size of "Default Server connectors", what is the role is this connector in mail size precedence? 

    LMS

    Thursday, October 4, 2018 6:02 AM
  • Hi LMSU,

    We do not know the mail flow in your environment, so we cannot know why it is not work in your environment, but here are the all limit with message size for Exchange, you can try one by one:

    Get-Mailbox user1 | fl *size*

    Get-TransportConfig | fl Max*size

    Get-ReceiveConnector | fl name, *size*

    By the way, If you want to block mails which send from external and size exceeds 20M, you can create a transport rule directly:

    Regards,

    Kyle Xu


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    Thursday, October 4, 2018 6:21 AM
  • Thanks Kyle

    We believe our question clearly mentioned current settings and our concern. Will explain it once again

    Below are our current settings:- (we tested multiple scenarios to accept mails with maximum 20 MB)

    ->Global Receive and Send message size (TransportConfig) is 28 MB (since we have security devices facing internet which received incoming mails, it will add additional overhead to 20 MB mails, so mentioned 28 MB as global size ) 

    -> Receive size with Default Frontend connectors of each server with 28 MB

    -> **Receive size with Default Server connectors with each server with 20 MB

    ** We need clarification with Default Server connectors. Our understanding with mail flow is external mails will be received by Default Frontend receive connectors (which accepts max 28 MB - the actual mail size might be around 20 MB), then the global size (transport configuration) will be applied and finally the Default Server Receive connector size will be applied. But in our case even though we change Default Server receive connector size to 10 or less, then also we continue to receive mails with 20 MB from outside.

    What we are looking exactly for "Order of precedence and placement of message size limits" with Exchange 2016 (the docs that we referred is not clear on Receive size with Default Server connectors - https://technet.microsoft.com/en-us/library/bb124345(v=exchg.150).aspx )   

    Hope it's clear to you and we will get some helpful comments on this.


    LMS

    Sunday, October 7, 2018 5:54 AM
  • Hi LMSU,

    It is related with the setting about mail flow in your organization, such as, mail archive connector, it will be limited by settings on connector first, then limited by organization configuration, then your mailbox.

    For more information about default mail flow, you can have a look about this article: Mail flow and the transport pipeline 

    Regards,

    Kyle Xu


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    Wednesday, October 17, 2018 2:33 AM
  • Hello

    As the document and Kyle mentioned, the 1st connector that will receive incoming mails will be named "Defaut Frontend your_server_name".

    This connector has a message size limit (as stated in MaxMessageSize property). And this value has to be the smallest one (comparing to other settings in your organization that limit messages size).

    An example below:

    your receive connectors (on each servers) have a MaxMessageSize value of 20 MB.
    your transport config MaxReceiveSize value should be between 20 and "anything bigger than 20"

    This is what means "order of precedence": the first element that will handle a "received" mail has to be the most restrictive regarding mail size.

    Otherwise it would be a non-sense to accept large mails on your Receive Connectors but block/limit them at transport level or even at mailbox level.

    Florent



    Wednesday, October 17, 2018 3:33 PM
  • Hi LMSU,

    Any update now?

    If the above suggestion helps, please be free to mark it as answer for helping more people.

    Regards,

    Kyle Xu


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Click here to learn more. Visit the dedicated forum to share, explore and talk to experts about Microsoft Teams.

    Tuesday, October 30, 2018 1:58 AM