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Exchange 2013 not honoring scoped connector when one recipient exists in second site

    Question

  • Two AD sites.

    Subnets are properly defined in AD.

    Two exchange servers.

    Server A in Site A sends to internet via scoped send connector to smarthost A.

    Server B in Site B sends to internet via scoped send connector to smarthost B.

    Mailflow between Server A and Server B is OK.

    Smarthosts use sender domain and WAN IP to allow relay.

    Smarthosts are separate providers.

    Users in Site A have email address @sitea.com.

    Users in Site B have email address @siteb.com.

    Neither smarthost A nor B can be configured to allow relay from the DOMAIN of the sender domain in the alternate site.

    User A in Site A with mailbox on Server A sends to internet, mail is routed out smarthost A.

    User A in Site A with mailbox on Server A sends to internet AND a user with a mailbox on Server B, mail for both recipients is routed out smarthost B.

    This is problem.  Relay is not permitted for the domain in the alternate site.

    Anyone know why mail is not honoring the scoped connector or how to prevent it?


    -=Chris

    Thursday, September 22, 2016 12:16 AM

Answers

  • I think what you are seeing is delayed fanout. Exchange will not bifurcate a message until the message reaches a fork in routing to save bandwidth. So the message isn't bifurcated until it reaches Site B.


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    • Marked as answer by Progent.CT Thursday, September 22, 2016 1:24 AM
    Thursday, September 22, 2016 1:10 AM

All replies

  • It's hard to answer a question specifically when it's phrased in generalities.

    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!

    Thursday, September 22, 2016 12:43 AM
    Moderator
  • I think what you are seeing is delayed fanout. Exchange will not bifurcate a message until the message reaches a fork in routing to save bandwidth. So the message isn't bifurcated until it reaches Site B.


    Blog:    Twitter:   

    • Marked as answer by Progent.CT Thursday, September 22, 2016 1:24 AM
    Thursday, September 22, 2016 1:10 AM
  • There's nothing general about it.  The behavior above is exactly what is happening.

    There are two exchange servers, each with a scoped send connector which routes mail to the internet.  Mail is not routing through the correct send connector to the internet.  It's routing to the internet, through the server in the other site.  But, it only does this when multiple recipients are specified and one of the recipients lives in the second site.


    -=Chris

    Thursday, September 22, 2016 1:13 AM
  • I think what you are seeing is delayed fanout. Exchange will not bifurcate a message until the message reaches a fork in routing to save bandwidth. So the message isn't bifurcated until it reaches Site B.


    Blog:    Twitter:   

    Beautiful!  Thank you!  My brief googling doesn't return any way to change this behavior.  I believe a consolidation of antispam/smarthost providers may be in order.  I didn't configure this, just troubleshooting it.  Right now each site has their own spam filtering. 

    -=Chris

    • Marked as answer by Progent.CT Thursday, September 22, 2016 1:23 AM
    • Unmarked as answer by Progent.CT Thursday, September 22, 2016 1:23 AM
    Thursday, September 22, 2016 1:23 AM