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Outbound Mail Flow theory question RRS feed

  • Question

  • Hello!

    https://technet.microsoft.com/EN-US/library/aa996349%28v=exchg.160%29.aspx

    4.

    1. What happens next depends on the configuration of the Send connector:

      • Default   The Transport service uses the Send connector you created to send the message to the Internet.

      • Outbound proxy   The Transport service uses the Send connector you created to send the message to the Front End Transport service on the local Mailbox server or on a remote Mailbox server. In the Front End Transport service, the default Receive connector named "Outbound Proxy Frontend <Mailbox server name>" accepts the message. The Front End Transport services sends the message to the Internet.

    Am I getting it right that the last sentence actually means "The Front End Transport services sends the message to the Internet using the same Send connector"? In other words, in the case of the Outbound proxy the Send connector is being used twice?

    Thank you in advance,

    Michael

    • Changed type Mike Crowley Wednesday, April 20, 2016 3:15 PM
    Thursday, November 19, 2015 10:16 AM

Answers

  • Hi Andy,

    "2015-10-26T18:23:35.649Z,08D298443A4EF31A,SMTP,outlook.com,>,Established connection to <CAS FET>"

    - this is the first connection with session  ID 08D298443A4EF31A

    2015-10-26T18:23:36.114Z,08D292B09C7B3ECF,SMTP,.outlook.com,+,Outbound proxy from <Mailbox Server> with session id 08D298443A4EF31A. Proxied session id 08D292B09C7B3ECE"

    - this is the second connection with session  ID 08D292B09C7B3ECE.

    As far as I understand each connection must be ruled by some connector - if there're two distinct connections there should be two connectors involved. But given that the checkbox "Proxy connection" is set on the Send connector's property page itself I think it means the both connections are made using the same Send connector, even if there's plenty of them.

    Thank you very much for the help!

    Regards,

    Michael


    Exactly. The same send connector is used for the connection to the CAS and the proxied connection *from* the CAS to the external mail server. The CAS Proxy is just a hop along the same path so to speak.

    Twitter!: Please Note: My Posts are provided “AS IS” without warranty of any kind, either expressed or implied.


    • Edited by Andy DavidMVP Wednesday, November 25, 2015 1:51 PM
    • Marked as answer by Mike Crowley Wednesday, April 20, 2016 3:16 PM
    Wednesday, November 25, 2015 1:51 PM

All replies

  • Hello!

    https://technet.microsoft.com/EN-US/library/aa996349%28v=exchg.160%29.aspx

    4.

    1. What happens next depends on the configuration of the Send connector:

      • Default   The Transport service uses the Send connector you created to send the message to the Internet.

      • Outbound proxy   The Transport service uses the Send connector you created to send the message to the Front End Transport service on the local Mailbox server or on a remote Mailbox server. In the Front End Transport service, the default Receive connector named "Outbound Proxy Frontend <Mailbox server name>" accepts the message. The Front End Transport services sends the message to the Internet.

    Am I getting it right that the last sentence actually means "The Front End Transport services sends the message to the Internet using the same Send connector"? In other words, in the case of the Outbound proxy the Send connector is being used twice?

    Thank you in advance,

    Michael


    Not twice, it simply proxies the message through a FET.

    Twitter!: Please Note: My Posts are provided “AS IS” without warranty of any kind, either expressed or implied.

    Thursday, November 19, 2015 12:16 PM
  • "it simply proxies the message" - what does mean "simply proxies"? Any "proxing" means the initial connection gets interrupted and then the new connection is created thus increasing the total number of connections. Exchange architecture assumes that any connection - both outbound or inbound - is being made via the corresponding connector, either outbound or inbound. This article clearly states the steps required for an outbound message to leave an Exchange organization:

    1) The Transport service uses the Send connector you created to send the message to the Front End Transport service on the local Mailbox server or on a remote Mailbox server.

    2) In the Front End Transport service, the default Receive connector named "Outbound Proxy Frontend <Mailbox server name>" accepts the message.

    3) The Front End Transport services sends the message to the Internet.

    Why the last step (step 3) does not have the corresponding connector? By what means "The Front End Transport services sends the message to the Internet"?

    Regards,

    Michael

    Thursday, November 19, 2015 2:57 PM
  • THe outbound connection will show the IP address of the FET and not the mailbox server that is sending the message using the send connector logic. Its really just a middle man.  What issue are you concerned about?

    Twitter!: Please Note: My Posts are provided “AS IS” without warranty of any kind, either expressed or implied.

    Thursday, November 19, 2015 3:53 PM
  • "What issue are you concerned about?" - no issue, I just want to know how it works. If Exchange documentation postulates that any out/in-bound traffic is being sent/received via connectors then the following statment -"The Front End Transport services sends the message to the Internet. " -  is at least not complete  because doesn't explain what connector is to be used.

    Judging by the picture above the same Send connector is used when making the second ("proxied") connection, but what if there are two or more Send connectors? Which OUTBOUND connector would be chosen and on what basis?

    Regards,

    Michael

    Friday, November 20, 2015 2:18 PM
  • The send connector used would be based on cost, address space, proximity. The same rules apply whether its proxied or not. The FET is stateless, so it has no queue.


    Twitter!: Please Note: My Posts are provided “AS IS” without warranty of any kind, either expressed or implied.

    Friday, November 20, 2015 6:24 PM
  • BTW, if you are wondering how this looks in the logs from both the MBX and proxied CAS:

    Mailbox Server:  ( 334648ba-0097-47ba-8fe0-d307a544c64f is the guid of the send connector used)

    2015-10-26T18:23:35.649Z,08D298443A4EF31A,SMTP,outlook.com,+,SmartHostConnectorDelivery 334648ba-0097-47ba-8fe0-d307a544c64f;QueueLength=TQ=1;RN=1;. 
    2015-10-26T18:23:35.649Z,08D298443A4EF31A,SMTP,outlook.com,>,"Outbound proxy via <CAS FET>
    2015-10-26T18:23:35.649Z,08D298443A4EF31A,SMTP,outlook.com,>,Established connection to <CAS FET>
    2015-10-26T18:23:36.649Z,08D298443A4EF31A,SMTP,outlook.com,-,Messages: 1 Bytes: 90434 ()

    CAS Role:

     2015-10-26T18:23:36.114Z,08D292B09C7B3ECF,SMTP,.outlook.com,+,Outbound proxy from <Mailbox Server> with session id 08D298443A4EF31A. Proxied session id 08D292B09C7B3ECE


    Twitter!: Please Note: My Posts are provided “AS IS” without warranty of any kind, either expressed or implied.



    Saturday, November 21, 2015 1:56 PM
  • Hi Andy,

    "2015-10-26T18:23:35.649Z,08D298443A4EF31A,SMTP,outlook.com,>,Established connection to <CAS FET>"

    - this is the first connection with session  ID 08D298443A4EF31A

    2015-10-26T18:23:36.114Z,08D292B09C7B3ECF,SMTP,.outlook.com,+,Outbound proxy from <Mailbox Server> with session id 08D298443A4EF31A. Proxied session id 08D292B09C7B3ECE"

    - this is the second connection with session  ID 08D292B09C7B3ECE.

    As far as I understand each connection must be ruled by some connector - if there're two distinct connections there should be two connectors involved. But given that the checkbox "Proxy connection" is set on the Send connector's property page itself I think it means the both connections are made using the same Send connector, even if there's plenty of them.

    Thank you very much for the help!

    Regards,

    Michael

    Wednesday, November 25, 2015 11:07 AM
  • Hi Andy,

    "2015-10-26T18:23:35.649Z,08D298443A4EF31A,SMTP,outlook.com,>,Established connection to <CAS FET>"

    - this is the first connection with session  ID 08D298443A4EF31A

    2015-10-26T18:23:36.114Z,08D292B09C7B3ECF,SMTP,.outlook.com,+,Outbound proxy from <Mailbox Server> with session id 08D298443A4EF31A. Proxied session id 08D292B09C7B3ECE"

    - this is the second connection with session  ID 08D292B09C7B3ECE.

    As far as I understand each connection must be ruled by some connector - if there're two distinct connections there should be two connectors involved. But given that the checkbox "Proxy connection" is set on the Send connector's property page itself I think it means the both connections are made using the same Send connector, even if there's plenty of them.

    Thank you very much for the help!

    Regards,

    Michael


    Exactly. The same send connector is used for the connection to the CAS and the proxied connection *from* the CAS to the external mail server. The CAS Proxy is just a hop along the same path so to speak.

    Twitter!: Please Note: My Posts are provided “AS IS” without warranty of any kind, either expressed or implied.


    • Edited by Andy DavidMVP Wednesday, November 25, 2015 1:51 PM
    • Marked as answer by Mike Crowley Wednesday, April 20, 2016 3:16 PM
    Wednesday, November 25, 2015 1:51 PM