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.
