Office 365: Configuring catch-all mailbox during migration

Step1: Create Catch-All Mailbox

1. Sign in to portal.office.com>Active Users

2. Create a new user named “Catch-All-Mailbox” and assign licenses either E1 or E3.

Step2: Create exception Security Group (Optional Step)

1. Log onto Office 365 admin portal

2. Go to Admin>Exchange>Recipients>Groups

3. Create a new Security Group named Catch-All-Exception

4. Add members to this group

Step3: Create a Transport Rule

5. Log onto Office 365 admin portal

6. Go to Admin>Exchange>Click “Mail Flow” icon, Click “Rules”

7. Click the “+” icon, then “Create a new rule”

8. As soon as the new rule box appears, click “More Options…” link towards the bottom of the page

9. Give rule a name, CatchAll-Mailbox Migration

10. Change the “apply this rule if…” to “The Sender is…”–>”Internal/External”–>”Outside this Organisation”

11. Change the “do the following…” to “Redirect the message to…”–>”These recipients”–> then select “Catch-All-Mailbox”

12. *OPTIONAL*  Click “Add Action” and then “Modify the message properties”–>”Set a message header”, then set the header to “X-Catchall-Migration-Rule” and value to “Yes”

13. Under “Except if”, Click “Add action” and then “If Recipient…”–>”Is this person”–>and select the “all” Group which contains all exclusions (this should be the “All” group which contains all users/groups INCLUDING the Catchall mailbox/group that you don’t want diverted)

14. Save

15. Once Migration is complete, delete the rule.