Unread messages occasionally not in inbox

Unread messages occasionally not in inbox

This issue has become quite irritating and problematic.

I have been finding emails in my Unread messages box that have not made their way to my inbox. I did not realize that there was a problem until about a week ago when I decided to check my Unreads and clear the box. I use ZOHO mail primarily for Customer Service issues for one of my companies so I was shocked to find unread customer service complaints in my Unread box that had never made it to my Inbox.

I just had another one. Luckily I have linked ZOHO mail to my Outlook. A customer complaint showed up in my Outlook.  I opened my ZOHO mail and the message in was not in my ZOHO mail inbox. I opened my Unread and there it was. I clicked on it to read and, of course, once I leave that message it is no longer "unread" so it is no longer in the UNREAD folder...but it is not in my inbox either. I looked in the "All Messages" folder and the message is there but it just never showed up in my inbox.

As you can imagine this is a real issue. I do not use Outlook for this company but have been forced to link to Outlook as a fail safe.

Any ideas why this is happening?