How to let gnus to fetch only newest email instead of fetching from the 1st one?

[Binjo]

Hi,

I'm using Gnus v5.13 under windows, with the following settings to read email:

(setq gnus-secondary-select-methods '((nntp "news.gmane.org")
(nnimap "gmail"
(nnimap-address "127.0.0.1")
(nnimap-server-port 9939)
;;(nnimap-stream ssl)
)
(nnml "another.pop.server")
))

(setq mail-sources
'((imap :server "127.0.0.1" ;;; stunnel to gmail
:port 9939
:user "binjo.cn"
:predicate "1:*"
:fetchflag "\\Seen")

(pop :server "another.pop.server"
:user "binjo"
:password "password")

))

The nnimap is OK for me to read & send email, whereas the pop is not working as
I expected. Whenever I start the gnus, it always fetch email from the 1st one,
not the newest one. And in my directory of "~/Mail/mail/misc", the filename is
still increasing, e.g last time fetched email is 123, this time it will be 124,
and this 124 is exactly the same to the 1 email...

I've tried to search via Google to resolve this, but with no luck. Is there any
settings I missed to let Gnus only fetch newest email?

Thanks in advance for your help.

Binjo

--
Life is like a prison, can you break it?