This happens not only in the web mail, but also the mobile app.

I have this one client whose subject mail is unsearchable. The subject always shows normal characters (non-unicoded) and not even the body of the email is searchable. This indicates that I somehow blocked her account, but no it's not.

So when I searched for the mail subject, it shows my replies AND her reply to mine. Never the initial/first email she sent to me.

I MUST always search for the first mail manually.

How do I fix this?