________________________________ From: centos-bounces at centos.org [mailto:centos-bounces at centos.org] On Behalf Of Don Knott Sent: Sunday, January 14, 2007 8:09 AM To: CentOS mailing list Subject: Re: [CentOS] Firewalling SMTP On 1/14/07, Denis Croombs <denis at croombs.org> wrote: I have a Centos server and I want to only accept mail for the local users from 3 mail servers, but I still want the users to be able to send emails through this server, If I firewall the SMTP port to my 3 mail servers is there any way users will be able to still send via the main POP server ? (currently using Sendmails SMTP-Auth) Thanks Denis ____________________________ I would setup SMTP-Auth and have sendmail ALSO listen on port 587 for users' to relay their mail. An external mail server would not attempt to deliver mail to a port other than 25. I'd use iptables to drop all connections to port 25 except for the 3 external hosts you want...problem solved. Mike