I think my scenario is a hybrid scenario, in that I have MX records pointing to Exchange 365, and all the internal company emails are in Exchange 365. However, we also have a couple of hundred other email which are simply redirects. Instead of moving them to 365, I want to leave them where they are, on a hosted MailEnable server.

Although I have got it working, it feel like my rule could be a lot easier.

My current rule is:

  • If recipient's domain is "mydomain.com"
  • Use the following connector: "redirect all mail to external server which also uses mydomain.com"
  • Except if: The recipient is: "list of 20 or so real email accounts"

The problem with this clumsy setup is that I must amend the list when I add a new user. Not the end of the world, but one more thing to forget.

I would prefer:

  • The recipient is located "outside the organisation"
  • Use the following connector "redirect all mail to external server which also uses mydomain.com"

The problem is the definition of what is considered "outside of the organisation". They are both using the same domain, which indicates both are inside, but my Exchange365 organisation has its Accepted Domain set as "Internal Relay", which AFAIK should allow what I want. Except it isn't.

What am I missing here? Or am I taking the wrong approach completely?

  • You don't have a Hybrid. A Hybrid entails federation between an on premises Exchange server and Exchange Online. What you're looking for is SMTP namespace sharing. Office 365 support is free. My suggestion is to open a support case from your O365 tenant and get them to assist you.
    – joeqwerty
    Dec 23, 2020 at 18:08
  • Thanks for the clarification on Hybrid. My past experience of Microsoft support is 4 days trying to explain something much simpler than this.
    – Greg Woods
    Dec 23, 2020 at 22:32
  • IME, Office 365 support is usually very prompt and usually very efficient in getting to the root of the issue and coming up with a resolution.
    – joeqwerty
    Dec 24, 2020 at 0:14
  • 1
    @joequerty - yes, I was very impressed by the Office 365 support. They phoned me back on time, understood the problem fully even before the call, already had the answer lined up, and stayed on the line with remote control until the rule was up and running. So thank you for the suggestion :)
    – Greg Woods
    Dec 26, 2020 at 12:24
  • Glad to help. I use Office 365 support a lot as I do quite a number of migrations every year and I've found their support to always be top notch.
    – joeqwerty
    Dec 26, 2020 at 15:43

2 Answers 2


You could create a distribution list which includes exception users, if you do this, you only need to add new users into this distribution list not modify the mail flow rule. enter image description here

  • A good suggestion, but there's a better option. See my answer
    – Greg Woods
    Dec 24, 2020 at 11:30
  • Thanks for your sharing:)You could mark your reply as best answer if other people encounter the same issue they could find the solution quickly:)
    – Joy Zhang
    Dec 25, 2020 at 5:18

The best answer is a Dynamic Distribution List. (Thanks to a Microsoft support call)

Setting up the dynamic distribution list

and then it is exactly the same as @joy-zhang suggested

using the distribution list in the mail flow rule

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