[fetchmail]fetchmail does not deliver when mail checked from different m

Hello!
I'm using fetchmail-5.7.4 with sendmail-8.11.3 on Mandrake 8.0, started as 
daemon at boot time
Sometimes, fetchmail does not fetch mails from my mailserver (postman), and 
as far as I know, this happens when I check my mail from a different machine 
on the mailserver, i.e., when I log in to postman and use mailx;
how does fetchmail mark emails as delivered (I use fetchmail -k, since I 
would like to have some mail on a different machine from time to time, too), 
does this not happen locally on my laptop, but on the remote mailserver?
Cheers,
TIm

-- 
Deep in the human mind there is a pervasive need for a logical universe
that makes sense. But the real universe  is always 
                                        one step beyond logic.

                                         - from "The Sayings of Muad'Dib"  
--                                               by the Princess of Irulan -
Tim Gruene, grune(_at_)embl-grenoble(_dot_)fr
EMBL Outstation Grenoble
6 Rue Jules Horowitz
BP 181
F-38042 Grenoble Cedex 9
France