To deliver mail to users' existing Google Workspace mailboxes and, at the same time, route a copy to Alumni Forwarding for only a specific group of users, set up a split (dual) delivery routing rule scoped by group membership. Members of the group are delivered to their mailbox and copied to Alumni Forwarding; everyone else is unaffected.
How this differs from "Route Unknown G Suite Users"
That article routes to Alumni Forwarding only when the mailbox does not exist. This article keeps normal mailbox delivery and adds a copy to Alumni Forwarding, limited to the members of a group you choose.
Below is a diagram showing the workflow.
⚠ SCREENSHOT NEEDED: New group split-delivery diagram (the existing Unknown Users diagram shows a different flow and should NOT be reused here).
Part 1 — Add the Alumni Forwarding mail route (host)
If you have already added the mx1.mailhop.org host for another route, reuse it and skip to Part 2.
1. Navigate to https://admin.google.com/ and login.
2. Navigate to https://admin.google.com/u/1/ac/apps/gmail/hosts
3. Click "ADD ROUTE".

4. Click this field.

5. Type "mx1.mailhop.org - Alumni Forwarding".
6. Click this field.

7. Type "mx1.mailhop.org".
8. Click here (Single host).

9. Click this field.

10. Type "25".
11. Click "Test TLS connection".

12. Click "SAVE".

Part 2 — Create the split delivery rule for the group
13. Navigate to https://admin.google.com/u/1/ac/apps/gmail/routing
14. Click "ADD ANOTHER RULE".

15. Click this field.

16. Type "Split delivery to Alumni Forwarding (group)".
17. Click inbound.

18. Click internal - receiving.

19. Under "For the above types of messages, do the following," select "Modify message".
⚠ SCREENSHOT NEEDED: Modify message selected
20. Scroll to "Also deliver to" and check "Add more recipients".
⚠ SCREENSHOT NEEDED: Add more recipients checkbox
21. Click "ADD".
22. Click the down arrow on the recipient and select "Advanced".
⚠ SCREENSHOT NEEDED: Recipient set to Advanced
23. Check "Change route" and select the "mx1.mailhop.org - Alumni Forwarding" route from Part 1.
⚠ SCREENSHOT NEEDED: Change route -> mx1.mailhop.org
24. (Recommended) Check "Suppress bounces from this recipient".
25. Click "SAVE" on the recipient.
26. Scroll to the Options section and check "Only affect specific envelope recipients".
27. In the recipient type drop-down, select "Group membership".
⚠ SCREENSHOT NEEDED: Envelope filter -> Group membership
28. Click "ADD" and select the group whose members should be split-delivered (for example an alumni@yourdomain.edu group). You can add more than one group.
⚠ SCREENSHOT NEEDED: Select group(s)
29. Click "SAVE" to save the rule.
⚠ SCREENSHOT NEEDED: Final rule SAVE
This completes the split (dual) delivery setup for the selected group. Mail to group members is delivered to their mailbox and copied to Alumni Forwarding; mail to non-members is delivered only to their mailbox.
Note: The Group membership filter affects both direct and child (nested) group members. Membership is managed from the Groups tab — adding or removing a user from the group adds or removes them from split delivery, with no change to the rule.
Part 3 — Partial group membership (a subset of a group)
Google applies the Group membership filter to the entire selected group (direct and child members); there is no option to select part of a group. To scope to a subset, use one of the following.
Method A — Create a dedicated sub-group (recommended)
30. Navigate to https://admin.google.com/u/1/ac/groups (the Groups tab).
31. Click "Create group".
32. Name it to reflect its purpose, e.g. "Alumni Forwarding - Split Delivery".
33. Add only the specific users who should receive split delivery.
⚠ SCREENSHOT NEEDED: Add members to the dedicated group
34. Click "Save" / "Done".
35. Return to the routing rule from Part 2 (or create a new rule following steps 13-25).
36. In Options, under "Only affect specific envelope recipients," select "Group membership" and choose the dedicated sub-group instead of the full group.
37. Click "SAVE".
Only the sub-group's members are split-delivered. You control the subset by managing that one group.
Method B — Pattern match or single recipients (small or ad-hoc subsets)
38. In Options, under "Only affect specific envelope recipients," select "Single recipient" for one address, or "Pattern match" for a regular expression.
⚠ SCREENSHOT NEEDED: Single recipient / Pattern match
39. Enter the address(es) or pattern identifying the subset.
40. Click "SAVE".
Use Method B for a handful of addresses or a pattern; use Method A for a defined, lasting population someone will maintain over time.
Testing
Send a test message from an external address to (1) a user in the group/subset — confirm it arrives in both the mailbox and Alumni Forwarding; and (2) a user not in the group — confirm it arrives only in the mailbox.
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