How to fix multiple emails that were read in outlook turning into unread automatically

A relative came to me with a weird issue in outlook, and he would receive an email, read it, it would turn into a read email and then suddenly, all the emails from that person would turn unread and be displayed in the inbox.

Weird indeed, I looked for flags in outlook client but couldn’t find any flag that would automatically switch emails to unread.

Also, the support where he worked couldn’t find anything to help him.

New information comes to light

The relative told me that he discovered that the issue occurred after he read the email on his mobile device (still using outlook) and then set that email to unread, which set all the emails from that sender to unread.

The solution to stop email switching to unread

With this new information, I understood what the issue was. In the mobile outlook, the display was “smart” with all the past emails of the sender, so when choosing to “set unread”, the outlook would turn all of the sender’s emails to unread.

So I disabled the smart grouping on the mobile outlook, and when setting the email to unread, it would set only that email.

After thought

The emails turning to unread, the way it happened here,  is a very specific situation, but since I couldn’t find any information on it, I thought I should write about it if someone has the same issue.