e-mail clients inside a VPN behind firewall
please go through the following situation.
i have some mail clients (Outlook as MUA in winXP) within a VPN (PPTP VPN Server running on a RedHat Server). clients are logging in to VPN from remote locations using dial-up. the VPN server is directly connected to internet through a firewall. also a squid caching proxy server is configured on the same RedHat server to serve internet to the VPN. firewall is restricting internel VPN clients from directly accessing outside services. email clients cannot be configured using any outside SMTP or POP3 servers directly.
there is no DNS server running inside the VPN. mail users are actually using the POP3 enabled e-mail service provided by the ISP. there are more than 100 mail clients having their e-mail account with the ISP.
1) is it possible to configure a Sendmail server on redhat Server and relay all outgoing mails directly to ISPs SMTP Server? is this require a working DNS server within the VPN?
2) if so what should be the exact configuration details in Outlook e-mail client? can i set the outgoing SMTP server as my RedHat box?
3) also i cannot configure e-mail clients using an outside POP3 server. is it possible to solve the problem by setting up a local POP3 server on the RedHat box? if no, please give me an alternate solution.