The problem is not solved yet.
First I tried to switch to MIME code as suggested, no help, CM2 does not recognize it.
Then I tried to configure Outlook express (instead of Netscape) to handle these PBEM moves. But now (maybe because of Norton) OE removes the attachment because it is "suspicious".
The way I can play is to go to removed attachment from which right mouse/properties/second page/more info (or something like that), copy it to notepad and save this to CM2 PBEM file.
Complicated.
And by the way removing .txt did not make it less suspicious.