>    From: Kai.Grossjohann@CS.Uni-Dortmund.DE (Kai Großjohann)
> 
>    > Is "Incoming" really the right group name?  Isn't it "nnml:Incoming"
>    > or something like this?
> 
> no, I use nnfolder and the group Incoming is displayed as 0: Incoming in
> the Group buffer.


It can be displayed like that even if it's real name is nnfolder:Incoming
if gnus-group-line-format uses %G rather than %g to display the group
name.  If that is the case, you still need to use the nnfolder
specifier (possibly nnfolder+mail: or whatever you set it up as).

Is that the case for you? If nnfolder is your "primary" select method,
then this doesn't really apply.