[fetchmail]nameserver failure

Please can anyone help me,

I've get often this message with Fetchmail;

nameserver failure ............. not flushed

But I want to have all mail.
The fetchmail -F don't work.
How can I force that Fetchmail retrieve all e-mail and let nothing behind at 
the provider?

+++++++++++++++

Greetings

Sirano De Berzherak

sirano_de_berzherak(_at_)hotmail(_dot_)com

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