I've got a user that has been having a weird issue for months that I just found out about but also can't figure out. Please note even though we're currently in a Hybrid configuration this issue existed before migrating his Mailbox to O365 and continues to exist post migration.
User is not having issues receiving email into his Inbox, except for one sender who is also part of our organization. The emails are not going into his Junk Email folder but rather into "Spambox." When one user emails him the email arrives into his Inbox for about 3-5 seconds before it is moved into Spambox. There is no Not Junk or other such options when you right-click in the folder to try and 'whitelist' the one sender. If you move the email back into the Inbox it is moved back again after a few seconds. This happens in OWA, Outlook 2013 and 2016, and his mobile device.
What have I checked?
- Spam Filter settings on Exchange Online itself
- Checked for anti-spam add-ins in Outlook, none found.
- Checked for anti-spam programs in Installed Programs, none found.
- Verified he has no additional Mailboxes or Email Accounts added.
- All other folks tested, both on-prem and Exchange Online Mailboxes, emails are delivered into the Inbox.
- Created new Windows and Outlook profiles on a blank computer, issue still occurs.
- Renamed the Spambox folder. This only had the email not show-up until renamed the folder back to Spambox and then the email showed up in his Inbox and was quickly moved to Spambox.
- No other user's reporting this problem and no other user's have a Spambox or Unwanted folders in either Outlook or OWA.