Skip to content

Microsoft 365 mail roundtrip

Setup guide

Using contacts is the easiest way to setup the mail roundtrip in Microsoft 365.

For this you create two contacts in Microsoft 365. One contact is allowed to receive the mail send by the InfraSonar roundtrip service and the other contact is used to forward the mail back to InfraSonar to close the roundtrip.

It is also possible to use a mailbox instated of a contact for receiving email and setup a forwarding rule on the mailbox. This requires you however to turn off allow external forwarding which is not a Microsoft best practice.

Create two contacts

  1. Open the Microsoft 365 admin center
  2. Open the users menu and then select contacts
  3. Click add contact to create a mail roundtrip contact for receiving emails
    1. Set Display name to: mailrountrip-receive (Feel free to pick a different name)
    2. Set Email to: mailrountrip-receive@example.org
    3. Enable: Hide from my organization's global address list
  4. Click add contact again to create the mail roundtrip contact forward to account
    1. Set Display name to: mailrountrip-infrasonar
    2. Set Email to: mail@mrt.infrasonar.com
    3. Enable: Hide from my organization's global address list

Setup rules

  1. Open the Exchange admin center
  2. Open the Mail flow menu and then select rules
  3. Click the Add rule button and select Create a new rule
  4. Name: InfraSonar mail roundtrip
  5. Apply this rule if: Select The recipient and then is this person
  6. Select the mailrountrip-receive contact you created before
  7. Do the following: Redirect the message to these recipients
  8. Select the mailrountrip-infrasonar contact you created before
  9. Click Next
  10. Leave the rule settings
  11. Review and Finish
  12. Ensure the rule is enabled!

Known issues

When your mail roundtrip is failing, logs are flooding or your admin mailbox get's spammed with error messages check the following.

Roundtrip mails are potential marked as spam

As our mail roundtrip is send at a regular interval changes are that our outgoing roundtrip message is flagged as spam.

Return mails are caught by outbound spam protection.

Microsoft 365 Outbound spam protection potentially identify the outbound messages as suspicious. As Microsoft 365 protection depends on your subscription we urge you to look at the official documentation on how to configure outbound spam protection according to your needs.