Configure Inbound Delivery Routing for Office 365

Document created by user.oxriBaJeN4 Employee on Sep 21, 2015Last modified by user.oxriBaJeN4 Employee on Apr 2, 2019
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This guide describes how to route messages from us to Office 365. It must be completed once your Mimecast account has been configured.


Bypassing Spam Checks


To ensure messages delivered from us to Office 365 aren't incorrectly identified as spam, resulting in delayed or failed email delivery, our service IP Ranges must be added to the allowed list in Office 365's Connection Filtering Policy.


To do this:

  1. Log on to the Office 365 Exchange Admin Center.
  2. Click on the Protection menu item.
  3. Click on the Connection Filter menu item.
  4. Click on the Edit icon.
    Connection Filter
  5. Click on the Connection Filtering menu item.
  6. Click on the + icon in the IP Allow list section:
    Connect Filter IP address
  7. Add the Inbound Mimecast IP Ranges. See the Adding Network Ranges to Office 365 page for further details.
  8. Click on the Enable Safe List option.
  9. Click on the Save button.


Determining the Host Name


Our delivery routes are configured to deliver all inbound messages to a specified hostname, which in this case is the MX record for the Office 365 account. To deliver messages from us to your Office 365 service, you must determine your hostname:

  1. Log on to the Office 365 Admin Center.
  2. Click on either the:
    • Domains menu item.
    • Setup | Domains menu item.
  3. Click on the Domain Settings for the domain you want to configure inbound delivery.
  4. Note the MX value.


Configure a Delivery Routing definition and policy to complete your inbound routing.


See Also...


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