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Need help with multiple SMTP connectors

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  • Need help with multiple SMTP connectors

    Hi all,

    I'm currently working on setting up multiple SMTP connectors to route outgoing e-mail through different smarthosts depending on the recipient and I need some help.

    First of all, the setup:
    We have one internet connection, and one leased line to main site. The main site owns the MX record and forwards the e-mail to our exchange on user-bases. (The server on the main site is a UNIX mDaemon). Both sites share the same e-mail domain ( and are connected with a leased line.

    Our exchange forwards all outgoing mail through the leased line to the main site. It has one SMTP connector with cost 1 and mail domain "*". The smarthost of that connector is also the mailserver on the main site. The 'Default SMTP Virtual Server' in "First Administrative Group/Servers/ExchangeServer/Protocols/SMTP" node is also configured to forward all mail with unresolved recipients to the same mailserver on the main site (tab "Messages", option "Forward all mail with unresolved recipients to host:".).

    Everything works fine.

    What I'm trying to do is setup two SMTP connectors as follows:

    "Outbound to Internet" connector.
    Cost: 10
    Mail domain: *
    Smarthost: mailserver at the ISP (internet line)

    "Outbound to Company" connector
    Cost: 5
    Maildomain: *
    Smarthost: mailserver at the main site (leased line)

    This -in my understanding- will send all the internet mail through the ISP, and all mail directed to (or es/uk/us/ ... through the main site. This will save some bandwidth on our leased line, which has a pretty high load 24/7.

    But when I set up the connectors like that I start getting NDR's when mailing to [email protected] if [email protected] is a user on the main site or if the user has a * address. So I'm only able to mail local users (my local store) and all internet adresses, but nothing on the main site...

    Can anyone help me out? This is the first time I'm trying to setup anything like that...

    Thnx in advance,


  • #2
    Re: Need help with multiple SMTP connectors

    The SMTP connector configuration would work, if you didn't have users on your own domain mixed - ie they were all located on your server.
    You are basically sharing the SMTP address space.

    Simon Butler
    Exchange MVP

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    • #3
      Re: Need help with multiple SMTP connectors

      Hi Simon,

      Thank you for the article - it works!

      I followed the instructions step by step, and everything works. Mail to * goes through the leased line, everything else is sent to the ISP.

      The thing I was doing wrong is that little 'allow messages to be relayed to these domains' checkbox on the properties of the SMTP connector - it needs to be checked for the * I also needed to create an additional recipient policy and clear the smarthost in "Forward all mail with unresolved recipients to host:" on "First Administrative Group/Servers/ExchangeServer/Protocols/SMTP/Default Virtual SMTP Server"

      Again, thank you for your help.