e-mail via gateway

I have 2 PCs: a Linux box (Debian Etch, kernel 2.6.15.4) and a notebook
(Windows XP HomeEdition). The Linux PC is connected both to the
internet via modem (ppp0) and to the notebook via NIC (eth0). On both
systems my browser is Firefox 1.5 and my e-mail client is Thunderbird
1.5; Using Samba I can share some regions....
On the Linux box a proxy (squid) is running; on both systems Firefox is
configured to use the "Manuell proxy connection" instead of "Direct
connection to net" - so I can browse the internet on both the PC and
the notebook.
My problem:
I can use the e-mail client on the Linux site but I cannot use it on
the notebook: it seems Thunderbird only connects "directly" instead via
LAN/proxy/socks/???
My first approach:
as done with Firefox I set Thunderbird's configuration to "Manuell
Proxy"; but squid doesn't understand SMTP / POP3. So I tried to
activate only the proxy-SOCKS-host in Thunderbirds preferences....no
success; I don't know what ever means "SOCKS host" in Thunderbird's
proxy settings - but it doesn't mean any connection to my (Linux)
socks-server (dante). Unlike Firefox I can't convince Thunderbird to
connect to my Linux system. Independently from settings in
Thunderbird's connection preferences panel, Thunderbird looks for it's
mail server on port 35 or where ever....
My goal:
to handle e-mails with Thunderbird on the notebook via the
Linux-PC/server/gateway/proxy7????

But I don't know how I can do that. Could anybody give me advice?
Thanks and sorry for my poor english.