I encountered two cases this week caused by the same bug. They began with different problem descriptions:

1. When people in a team send meeting requests to a room mailbox their team regularly uses, they receive an NDR for a person who left the company some time ago and no longer has an account or mailbox
2. A person who used to be the delegate/manager for a room mailbox continues to receive meeting requests for that room, even though they no longer appear in the delegates list

Note that this doesn’t only impact room mailboxes, it just happens that was the situation in both of my cases this week.

In both cases the same bug was the root cause.  When delegates are added to a mailbox an invisible rule is added to that mailbox to forward the meeting requests to the delegates. When they are later removed the rule continues to send them the meeting requests.

For example in this case Ana Williams has one delegate, Alan Reid, but a former delegate Alex Heyne is also still receiving a copy of the meeting requests, even though he does not appear in the delegates list.

Because the invisible rule is invisible it can’t be seen in Outlook.

Instead we need to open the mailbox using MFCMAPI to see the rule.

Update: a few people have let me know that they’ve had success fixing this issue by simply removing all existing delegates, then re-adding them. That seems to remove the invisible rule with the stale entry, and then it is re-added with just the intended delegates. Though that approach didn’t work for me in these cases, it would be the quickest win so is worth trying first before going further with MFCMAPI.

Download MFCMAPI here and extract the file onto a computer that also has Outlook installed (it will use the Outlook profile to logon to Exchange).

After launching MFCMAPI click the Session menu and choose Logon.

After logging on choose MDB, Open other mailboxes, then From GAL.

Choose the suspect mailbox from the GAL, in this case Ana Williams. Click OK at the “CreateStoreEntryID flags” dialog that appears.

Navigate the Root Container down to Top of Information Store and then Inbox. Right-click Inbox and choose Other tables and then Rules table.

Depending on the number of regular inbox rules the mailbox has you may see more than one entry. To locate the invisible rule that handles email forwarding for delegates look for the rule that has a blank “Rule Name“, and has a PR_RULE_PROVIDER value of “Schedule+ EMS Interface“.

Before proceeding to the next step be aware that this process removes the email forwarding for all delegates on the mailbox. So before you delete it make sure you’ve made a note of the delegates who are supposed to remain on the mailbox, as they will need to be re-added.

Right-click the rule and choose Delete.

The final step is to re-add any delegates to the mailbox that are still wanted.

When this is complete only those intended delegates will receive the meeting requests, and the deleted delegates should receive no more meeting requests, or in the case of the former staff member, no longer cause NDRs back to the meeting organizers.