verify signature from Windows and Ubuntu does not work

[Mike]

Hi

I use IMAP for my mailbox and I am accessing this from Win/Outlook and
Ubuntu/Evolution.

When I get an email and I access it first with Outlook, then I can not
verify the signature anymore in Ubuntu as the whole email got detached
into a separate attachment.

How can I resolve this?
I could not find any options in gpg4win or kleopatra.
--
Thanks for any hint
Mike