version 10.4R7.5;
system {
    host-name srx210;
    root-authentication {
        encrypted-password "$1$WWS6alX0$DPbw8ydPeEC0g0AmaqfO20"; ## SECRET-DATA
    }
    name-server {
        203.0.178.191;
        203.215.29.191;
    }
    services {
        ssh {
            root-login deny;
        }
        xnm-clear-text;
        web-management {
            http {
                interface vlan.0;
            }
            https {
                system-generated-certificate;
                interface vlan.0;
            }
        }
    }
    syslog {
        archive size 100k files 3;
        user * {
            any emergency;
        }
        file messages {
            any critical;
            authorization info;
        }
        file interactive-commands {
            interactive-commands error;
        }
    }
    max-configurations-on-flash 5;
    max-configuration-rollbacks 5;
    license {
        autoupdate {
            url https://ae1.juniper.net/junos/key_retrieval;
        }
    }
    ntp {
        boot-server 203.0.178.191;
        server 203.0.178.191;
    }
}
interfaces {
    interface-range lan {
        member ge-0/0/0;
        member ge-0/0/1;
        member fe-0/0/2;
        member fe-0/0/3;
        member fe-0/0/4;
        member fe-0/0/5;
        member fe-0/0/6;
        member fe-0/0/7;
        unit 0 {
            family ethernet-switching {
                vlan {
                    members vlan-trust;
                }
            }
        }
    }
    at-1/0/0 {
        mtu 1492;
        encapsulation ethernet-over-atm;
        atm-options {
            vpi 8;
        }
        unit 0 {
            encapsulation ppp-over-ether-over-atm-llc;
            vci 8.35;
        }
    }
    lo0 {
        unit 0 {
            family inet {
                address 127.0.0.1/32;
            }
        }
    }
    pp0 {
        unit 0 {
            point-to-point;
            ppp-options {
                chap {
                    default-chap-secret "$9$Nhbs4ZGi.fTHqmTF3tp-VbYJGkqf"; ## SECRET-DATA
                    local-name xxxxxx; //ADSL ISP Username
                    passive;
                }
            }
            pppoe-options {
                underlying-interface at-1/0/0.0;
                auto-reconnect 1;
                client;
            }
            family inet {
                address xxx.xxx.xxx.xxx/32; //Public Address
            }
        }
    }
    vlan {
        unit 0 {
            family inet {
                address 192.168.1.1/24;
            }
        }
    }
}
routing-options {
    static {
        route 0.0.0.0/0 {
            next-hop pp0.0;
            metric 0;
        }
    }
}
protocols {
    stp;
}
security {
    nat {
        source {
            rule-set trust-to-untrust {
                from zone trust;
                to zone untrust;
                rule source-nat-rule {
                    match {
                        source-address 0.0.0.0/0;
                        destination-address 0.0.0.0/0;
                    }
                    then {
                        source-nat {
                            interface;
                        }
                    }
                }
            }
        }
        destination {
            pool dnat-server {
                address 191.168.1.10/32;
            }
            rule-set dnat {
                from zone untrust;
                rule rule-server {
                    match {
                        destination-address xxx.xxx.xxx.xxx/32; //Public Address
                        destination-port 25;
                    }
                    then {
                        destination-nat pool dnat-server;
                    }
                }
            }
        }
        proxy-arp {
            interface pp0.0 {
                address {
                    192.168.1.10/32;
                }
            }
        }
    }
    screen {
        ids-option untrust-screen {
            icmp {
                ping-death;
            }
            ip {
                source-route-option;
                tear-drop;
            }
            tcp {
                syn-flood {
                    alarm-threshold 1024;
                    attack-threshold 200;
                    source-threshold 1024;
                    destination-threshold 2048;
                    timeout 20;
                }
                land;
            }
        }
    }
    zones {
        security-zone trust {
            address-book {
                address mainserver 192.168.1.10/32;
            }
            host-inbound-traffic {
                system-services {
                    all;
                }
                protocols {
                    all;
                }
            }
            interfaces {
                vlan.0;
            }
        }
        security-zone untrust {
            screen untrust-screen;
            interfaces {
                at-1/0/0.0;
                pp0.0;
            }
        }
    }
    policies {
        from-zone trust to-zone untrust {
            policy trust-to-untrust {
                match {
                    source-address any;
                    destination-address any;
                    application any;
                }
                then {
                    permit;
                }
            }
        }
        from-zone untrust to-zone trust {
            policy static-nat {
                match {
                    source-address any;
                    destination-address mainserver;
                    application junos-smtp;
                }
                then {
                    permit;
                }
            }
            policy default-deny {
                match {
                    source-address any;
                    destination-address any;
                    application any;
                }
                then {
                    deny;
                }
            }
        }
    }
    alg {
        dns disable;
    }
    flow {
        allow-dns-reply;
        tcp-mss {
            all-tcp {
                mss 1300;
            }
        }
    }
}
vlans {
    vlan-trust {
        vlan-id 3;
        l3-interface vlan.0;
    }
}

[edit]
root@srx210#