Do these steps to create a rule in Microsoft Exchange Online:

1. Go to the Exchange Admin Center.
2. Click mail Mail flow in the menu on the left.
3. Click Rules.
4. Click add Add a rule.
5. Click Create a new rule.
6. Enter Zivver: Secure message by sender + Outbound DLP as the name of the rule.
7. Under Apply this rule if *, select The sender.
8. Under Select one, select is external/internal.
9. Select Inside the organization.
10. Click Save.
11. Click the add button under the Apply this rule if * section.
12. Under And, select The sender.
13. Under Select one, select domain is.
14. Enter every sending domain and click Add.
15. After all domains are added, click Save.
16. Click the add button under the Apply this rule if * section.
17. Under And, select The subject or body.
18. Under Select one, select subject matches these text patterns.
19. Enter (?i)\[secure\].
    
    Tip

    The regex (?i) makes the match case-insensitive.
20. Click Add.
21. Enter (?i)\[secure\s?email\].
22. Click Add.
23. Enter (?i)secure\s?email.
24. Click Add.
25. Click Save.
26. Under Do the following *, select Modify the message properties.
27. Under Select one, select set a message header.
28. Click the first Enter text field.
29. Enter zivver-relay.
30. Click Save.
31. Click the second Enter text field.
32. Enter smart-sender.
33. Click Save.
34. Click the add button under the Do the following * section.
35. Under Add, select Redirect the message to.
36. Under Select one, select the following connector.
37. Select Zivver Send Connector.
38. Click Save.
39. Under Except if, select The message headers….
40. Under Select one, select matches these text patterns.
41. Click Enter text.
42. Enter skip-zivver-relay.
43. Click Save.
44. Click Enter words.
45. Enter true.
46. Click Add.
47. Click Save.
48. Click Next.
49. Enable the option Stop processing more rules.
50. Enable the option Defer the message if rule processing doesn’t complete.
51. Set Match sender address in message to Envelope.
52. Enter the follwing text in the Comments section:

Allow users to deliberately send secure messages via Zivver using a specified email property. For example, a keyword (e.g. ‘[secure]’ in the subject line) or standard email attribute (e.g. a Microsoft Purview sensitivity label applied to the email by the user).

52. Click Next.
53. Click Finish.
54. Click Done.

The rule is now created but not enabled yet. Make sure the priority of all existing rules is correct. If the message must be processed by other rules first, make sure the Encryption Gateway rule has a lower priority.

Since the rule is not enabled yet, no outbound message that matches the filter will be submitted to the Zivver SMTP server. Only enable the rule once you’re certain all rule priorities are configured correctly.