Mail inbox aut. deleted after reading.

[Hans]

When i have read a mail the mail stay's in the inbox, but when i then go to
an other folder and come back in the "inbox" folder the mail is gone!

What can i do about this?

 

[mac]

When i have read a mail the mail stay's in the inbox, but when i then go
to an other folder and come back in the "inbox" folder the mail is gone!

What can i do about this?

While viewing the Inbox, go to View menu>current view>select Show all
Messages.