Do these steps to create a rule in Microsoft Exchange On premise:

1. Go to the Exchange Administrative Center (EAC).
2. Log into EAC as an administrator.
3. Go to mail flow in the menu on the left.
4. Go to rules.
5. Click the add button.
6. Click Create a new rule….
7. Give the rule a name.
   For example: Zivver Encryption Gateway.
8. On the bottom, click on More options….
9. Under *Apply this rule if… select The subject or body… and then subject includes any of these words.

10. Add a word or phrase.
    For example: Secure.
    

    You can include the regex (?i) to make the check case insensitve.
    For example: (?i)Secure.

11. Click the add button.

12. Click OK.

13. Under *Do the following select Redirect the message to… and then these recipients.

14. Look up the contact person that was created previously and select it.

15. Click add ->.

16. Click OK.

17. Under Except if… click add exception.

18. Select A message header… and then matches these text patterns.

19. Click on *Enter text….

20. Enter X-Zivver-Transport.

21. Click OK.

22. Click *Enter text patterns….

23. Enter ..*. (That is 2 dots, 1 asterisk/wildcard, 1 dot).

24. Click the add button.

25. Click OK.

26. Select for Choose a mode for this rule the option Enforce.

27. Enable the option Defer the message if rule processing doesn’t complete.
    If you enable this option, a message will not leave Exchange until the message has been checked by this rule. If for any reason Exchange temporarily does not check messages for this rule, processing these messages will be paused.

28. Click Save.

The Mail Flow Rule is now set. Please make sure that the priority of all existing rules is correct. If the sent message needs to be processed by other rules first, please make sure that the rule created for Encryption Gateway has a lower prioirty.

Any outbound message that matches the filter will be submitted to the Zivver SMTP Server. If this is not desirable, please deactivate the rule.