review the fetchmail man page; you need the capital K option:
-k | --keep
(Keyword: keep) Keep retrieved messages on the remote mailserver.
-K | --nokeep
(Keyword: nokeep) Delete retrieved messages from the remote mailserver.
-U | --uidl
(Keyword: uidl) Force UIDL use (effective only with POP3).
Force client-side tracking of 'newness' of messages (UIDL
stands for ''unique ID listing'' and is described in RFC1725). |