Shared smtp address space RRS feed

  • Question

  • Hello,

    I'm starting to look at the whole office 365 offerings but have a couple of questions somebody may be able to help me with.

    Q1) My company runs of a shared smtp address space and what I mean by this is the company has to separate AD forests each with it's own Exchange server forest deployed. There is a domain trust between the two but email flow is totally separate. The address space we both use (@abc.com) is however shared and the mx records point to  cloud service provider who's role is to detect Spam, Viruses and other not business emails. They will then by means of AD query determine if the email is for a recipients on the US side or a recipient on the UK side. This is how emails is delivered to both Exchange forests while sharing a single smtp address space.

    So with this in-mind how do we maintain the separation and still have email flow independently?

    Q2) I mentioned above that we use a cloud service provider who sits before both Forests but I'm not sure is I could continue to operate with the cloud being the first inbound hop with 365?

    Q3) So we both operate two separate AD structures with like I said a trust between the two. Given that AD-FS is required for authentication and given this would be setup to a single AD instance how to we work regards the second AD forest?

    Q4) My onsite Sfb deployment also integrates heavily with my Cisco call systems and onsite PBX's for 30 plus sites and I wonder what if any integration to my in-house telephone system could be preserved having migrated Sfb and Exchange to 365.

    Q5) I also use a third party product for the replication of contacts and FreeBusy information with several other Exchange forests in which no AD trust is in-place. How can I continue to provide this information in a 365 setup especially since the other Exchange forests also send email as  @abc.com albeit from yet again a totally separate Exchange forest.? E-,ail routed inbound to these domains also goes through the cloud service provider.

    Many thanks


    Saturday, February 25, 2017 3:50 PM


  • You seem to have a complex environment. The best would be to have a consultant go through your environment to give the best recommendations. I am outlining the basic idea on what can be done based on the information you provided. 

    1.You would have to consider integrating both forests to a single tenant. The process would be to use Hybrid within each forest & migrate in a phased manner.

    Check the link below for requirements.


    2.Most of the Gateway filters like Mimecast,Proofpoint do work fine with O365, you can set the delivery route to O365 once you complete the migration. You may want to check with your respective vendor for configuration supported.

    3.As long as you have a trust in place & unique UPNs,you could have one ADFS farm servicing multi forests.


    4.For Federated sharing you would already have a Federated trust with MFG. You may want to create an Organisation relationship with the external partners in O365.


    5.You can implement a hybrid solution using your existing Skype for Business Server deployment and PSTN connectivity. In this topology, users are homed in the cloud on Skype for Business Online instead of being homed on the on-premises deployment. You can choose this option if you currently have users homed in the cloud or if you want to start migrating users to the cloud.
    With this option, your Skype for Business Online users get their PSTN connectivity through Enterprise Voice on your on-premises Skype for Business Server deployment, with Skype for Business call control in the cloud.



    • Proposed as answer by Allen_WangJF Tuesday, February 28, 2017 3:19 PM
    • Marked as answer by leslie hill Tuesday, February 28, 2017 8:03 PM
    Monday, February 27, 2017 1:24 AM