Argh! (Adelphia, E-mail, iptables, etc.)

[Dan Jenkins]

Here is the solution I've created for some folk on Adelphia & Comcast.

I have an an email server running Postfix on a T1 connection to 
relay through. I use Postfix. Sendmail, qmail, exim, etc. ought to
work similarly. Details are left as an exercise for the reader. ;-)

===================================
Overview:
    Restricted server (on Adelphia) receives email on port 10025
    Server on unrestricted network accepts email for and transports
      it to restrcited server.
    Change DNS MX record to send email through unrestricted server.

===================================
On restricted (Adelphia) server make these changes:
  Modify /etc/postfix/master.cf:
   Add line:
     10025   inet    n       -       y       -       -       smtpd
  Reload postfix configuration with 'postfix reload'

  Test it is listening on port 10025:
     telnet localhost 10025
    make sure you get SMTP prompt (220 host.name ESTMP, for example)

===================================
On unrestricted server make these changes:
  Modify /etc/postfix/main.cf:
   Add line:
     transport_maps = hash:/etc/postfix/master.cf
   Add to:
     relay_domains  = ... domain.to.relay
     Note: Do NOT add to mydestinations
   Add to:
     smtp_recipient_restrictions = ... permit_mx_backup

  Modify /etc/postfix/transport:
   Add line:
     domain.to.relay   smtp:[host.to.relay.to:10025]

  Run 'postmap /etc/postfix/transport'
  Reload postfix configuration with 'postfix reload'

===================================
  Change DNS MX record for domain.to.relay to point at
    unrestricted server.

  Note: Issues such as host.to.relay.to being a dynamic IP
        are beyond the scope of this. ;-)

Hope this helps someone.

-- 
Dan Jenkins (dan at rastech.com)
Rastech Inc., Bedford, NH, USA --- 1-603-624-7272
*** Technical Support for over a Quarter Century