SMTP Email DLP with Office 365

  • 19 April 2023
  • 1 reply

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Microsoft rolled out an unannounced change earlier this year to newly created Office 365 tenants, which disables the ability to create Inbound exchange 'On-premises to O365'.  Inbound Connector Restricted Imposed by Exchange Online (


I have been working with Microsoft to attempt to enable this connector type for a developer M365 tenant, but they are reluctant to do so.  Initially they attempted to have me try the new Partner Org to O365 inbound connector, which raised SMTP 451 errors in Skope IT.


Now their reply has been to:


"We really need for you to contact Netskope to ask them for the certificate domain, the requirements for creating the inbound connect is in place for a few months now and most likely Netskope have the certificates ready which they can provide if a customer ask them for it”


Since this only effects customers that would be using M365 end to end, I am not sure if Netskope has seen or heard of this issue yet.  The Docs site still references using the 'On-premises to O365' connector type to direct email from Netskope back to 0365. 

Is Netskope working to address the connector restrictions Microsoft has imposed, or is there language that can be provided back to MS support to have the legacy 'On-premises to O365'. 


I know Netskope isn't the only security product that needs the legacy 'On-premises to O365', connector type, and surprised MS hasn't reversed course with their unannounced decision to provide tech partners time to make the switch on their end.  

1 reply

Badge +5

Thanks for mentioning this article. Netskope does not seem to have an alliance with M365. 

If we need to succeed at features that rely on third-party platforms such as M365, then repeat documentation, new videos,etc. needs to be posted often. 


Often times we have observed that Microsoft changes documentation and then the previous config is not valid anymore or is not reflected in the documentation. 

examples of it are:


1. SSO with Azure

2. Reverse Proxy 

3. CASB Microsoft

4. Email DLP


Microsoft's pace seems to be too high for anyone to catchup to them. They are trying to win over everyone by releasing new features everyday.