What's Happened To My Emails?

[MichaelZZ]

I am new to GMX and I'm still getting to grips with all its features although I've been using other email programs for many years.
I hope you can help with a problem I encountered yesterday:
When I went to my GMX Inbox, I saw that I had 4 new emails, with as usual, the headings in bold type. I didn't open any of these emails immediately but left the Inbox screen open. After a few minutes, the Inbox entries cleared and the emails had disappeared. Fortunately, I run a mail collector service (Windows Mail) and the messages were there but I would like to be able to keep my GMX messages in my GMX inbox. Is there some setting, either within Windows Mail or within GMX, that I have set incorrectly?
I would appreciate any advice!
Thanks in advance.

[MichaelZZ]

Ok, panic over!
I've found the check box "Leave a copy of messages on Server" on the Windows Mail "Advanced" tab.