Emails are automatically marked as read after a few seconds I have a problem that potentially causes me to miss important email: An incoming message is automatically marked as read after a few seconds. One can watch how a new email is at first unread in the inbox and then turns to read.
This problem seems to occur only for one of several IMAP accounts. 

My settings are: In the viewing tab a selection "Mark all messages as read when opening a conversation" check box is unset.

What could cause this?
How can I diagnose if the problem is on the server side or if Mail.app is malfunctioning?
I've been able to fix the issue: In fact, it was the fault of OS X Server.



In the server app, under the calendar tab, there is a checkbox "activate invitations via e-mail". The problem disappeared when I unchecked it!