fetchmail, postfix, cyrus imap folder

[torgan]

Hi,
i got a problem with a cyrus, postfix, fetchmail configuration on my server.
Well the story is simple and maybe the answer, too.
I´m using following configuration and i hope i don´t forget anything.
I got postfix 2.0  installed, with cyrus imap 2 on a freebsd 4.10 system.
The simpliest thing i want to do is fetchmail from my isp mails and put 
it to my cyrus imap folder.
And it works, but now comes my question:
When i do fetchmail first time my isp mailserver the mails will be 
delivered to my cyrus imap folder.
 So long everything is oki, but sometimes i´m a stupid boy a delete some 
mails in the imap folder that after a week or so i want to read again.
I was so smart to not let fetchmail delete my mails (keep) and than 
comes it the way i can´t explain to myself.
When i do a second fetchmail to the isp server the old mails i´ve 
already delete in the cyrus imap folder will not be saved again ???
Y that ?
Is there something i don´t get into my mind or is this the way cyrus 
handles the imap folder ?  Deleted mails will never come through cyrus 
to my imap folder again ???

Can somebody explain it to me or give me just a hint to an RFC where i 
can find the answer ?
Thanks for reading
greetz

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