Are you struggling with duplicate emails keep coming to junk folder in Exchange Online? You’re in the right place.
Here’s how we resolved the issue:
For some reason, a shared mailbox in Exchange online started receiving duplicate emails to the junk folder and it keeps increasing. Message trace shows only one email sent to the mailbox.
We didn’t block the sender since no message traces found and we think the blocking won’t help.
We created a rule via owa to keep the emails in the deleted items folder instead of junk folder. Guess what, it doesn’t work as well.
The emails keep coming up even we delete them. The shared mailbox is configured by using 6 months cache policy and applied to all users in the organization via a group policy so it’s difficult for us to remove or modify the policy to check the status using an online version.
Junk folder also been deleted by using MFCMAPI but it gets created back by design.
The full access permission was removed in the shared mailbox permission and granted to only one admin to check the status but no luck.
We thought of moving the mailbox to another database using New-MoveRequest command but it didn’t work since the mailbox has huge folders and it’s beyond the limit.
We also thought of removing the shared mailbox from the affected users’ Outlook, deleting the junk email, and then re-adding Mailbox but we didn’t try it since we are not very sure if this will fix it. The shared mailbox is accessed by multiple users and its really difficult to ensure that they removed and re-added the mailbox.
My brain suggests to create a new shared mailbox with the same email address and move the messages from the affected mailbox but I was afraid to try this because what if not all items copied to the new mailbox just like new-moverequest command.
Finally, we disabled mail protocols (POP, IMAP, Exchange web services and activesync) and kept only OWA and MAPI on the affected mailbox using the admin portal. We then hard deleted emails using MFCMAPI, previously used OWA. Guess what, emails stopped coming to the junk folder.
Disable Mail Protocols
- Access Exchange admin center
- Go to Recipients > Mailboxes
- Select the mailbox you want to disable mail protocols for
- On the General tab, under Email apps & mobile devices, select Manage email apps settings.
- In the Manage settings for email apps display pane, set the email protocols to Disabled.
- Click save.
Delete Emails Using MFCMAPI
- Download MFCMAPI. Access it.
- Go to “Tools” > “Options”.
- Make sure that “Use the MDB_ONLINE flag when calling OpenMsgStore”
- And “Use the MAPI_NO_CACHE flag when calling OpenEntry” are checked. Click “OK”.
- Click on “Session” > “Logon”.
- Choose the Outlook profile contains the emails you want to delete > “OK”.
- Double click the profile with emails you want to delete.
- Expand “Root Container” > Scroll down > Expand “Top of Information Store”
- Right-click “Junk Email” and select “Advanced” and select “Empty items and subfolders from folder…”
- Check the “Hard Deletion” and “Delete associated (hidden) items and click “OK”.
After implementing these steps and monitoring the situation for a couple of weeks, the issue was resolved, and the duplicate emails keep coming to junk folder stopped.
This solution effectively addressed the problem of duplicate emails keep coming to junk folder. If you encounter a similar issue, try these steps to resolve it.