Re: Simple Python script as SMTP server for outgoing e-mails?

Date	2013-07-22 08:21 -0600
From	Michael Torrie <torriem@gmail.com>
Subject	Re: Simple Python script as SMTP server for outgoing e-mails?
References	<gksnu85fe69utl50s4e1tik0bhinndls3m@4ax.com> <kshi6l$lvc$1@reader2.panix.com> <tp8qu81vrhft7o89dp9551ju49t2i0a5nv@4ax.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.4981.1374502869.3114.python-list@python.org> (permalink)

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On 07/22/2013 06:19 AM, Gilles wrote:
> On Sun, 21 Jul 2013 21:01:09 +0000 (UTC), Grant Edwards
> <invalid@invalid.invalid> wrote:
>> Unless you've got a static IP address, a domain name, and a valid MX
>> record that will match up when they do a reverse DNS lookup, it's
>> pretty unlikely that you're going to have much luck running an SMTP
>> server.  Most other SMTP servers are probably going to ignore or
>> reject your attempts to transfer mail from your own SMTP server.
> 
> Incidently, how do ISP MTAs find whether the remote MTA is legit or
> running on some regular user's computer?
> 
> 1. Query Reverse DNS for IP
> 2. Find domain
> 3. Query DNS for MX
> 4. ?

My mail server did a number of things:
1. ensure IP address of sending server has a reverse name (domain didn't
particularly matter)
2. ensure the HELO address in SMTP matches IP address of sending server
3. check sender IP address against spam blacklists, which includes
netblocks of home ISPs, some entire countries, flagged subnets
4. greylist sender IP if the recipient requested it.  First connection
always fails with a nonfatal server error, next connection must wait at
least 5 minutes.  If a reconnection happened too quickly, the IP was
temporarily black listed.  After success, IP address is whitelisted for
a time.  A commandline MTA will not be able to get through greylisting;
only a mail server with queuing could.  Spambots tend to give up on the
first error, even now. Cheaper targets I guess.
5. spamassassin checked SPF (DNS) and domainkeys (message itself) and
weighted the spam factor accordingly

I think there were other basic rules that sendmail applied to the
sender, but I can't remember all of what they are.  This is well and
truly off topic now for the python list, though.

Thread

Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-07-21 16:42 +0200
  Re: Simple Python script as SMTP server for outgoing e-mails? Chris Angelico <rosuav@gmail.com> - 2013-07-22 00:48 +1000
    Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-07-21 18:19 +0200
      Re: Simple Python script as SMTP server for outgoing e-mails? Michael Torrie <torriem@gmail.com> - 2013-07-21 11:46 -0600
        Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-07-21 22:34 +0200
          Re: Simple Python script as SMTP server for outgoing e-mails? Ivan Shmakov <oneingray@gmail.com> - 2013-07-21 20:53 +0000
          Re: Simple Python script as SMTP server for outgoing e-mails? Michael Torrie <torriem@gmail.com> - 2013-07-21 18:28 -0600
            Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-07-22 14:11 +0200
              Re: Simple Python script as SMTP server for outgoing e-mails? Chris Angelico <rosuav@gmail.com> - 2013-07-22 22:29 +1000
                Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-07-22 14:38 +0200
                Re: Simple Python script as SMTP server for outgoing e-mails? Chris Angelico <rosuav@gmail.com> - 2013-07-22 22:51 +1000
                Re: Simple Python script as SMTP server for outgoing e-mails? Michael Torrie <torriem@gmail.com> - 2013-07-22 08:08 -0600
                Re: Simple Python script as SMTP server for outgoing e-mails? Chris Angelico <rosuav@gmail.com> - 2013-07-23 00:15 +1000
                Re: Simple Python script as SMTP server for outgoing e-mails? Duncan Booth <duncan.booth@invalid.invalid> - 2013-07-23 08:06 +0000
                Re: Simple Python script as SMTP server for outgoing e-mails? Chris Angelico <rosuav@gmail.com> - 2013-07-23 19:19 +1000
                Re: Simple Python script as SMTP server for outgoing e-mails? Duncan Booth <duncan.booth@invalid.invalid> - 2013-07-23 10:06 +0000
                Strange behaviour with os.linesep Vincent Vande Vyvre <vincent.vandevyvre@swing.be> - 2013-07-23 13:42 +0200
                Re: Strange behaviour with os.linesep Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-23 15:25 +0000
                Re: Strange behaviour with os.linesep Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-07-23 19:41 -0400
                Re: Strange behaviour with os.linesep Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-07-23 19:51 -0400
                Re: Strange behaviour with os.linesep Vincent Vande Vyvre <vincent.vandevyvre@swing.be> - 2013-07-24 09:02 +0200
                Re: Strange behaviour with os.linesep Chris Angelico <rosuav@gmail.com> - 2013-07-24 17:39 +1000
                Re: Strange behaviour with os.linesep Terry Reedy <tjreedy@udel.edu> - 2013-07-24 12:01 -0400
                Re: Strange behaviour with os.linesep Jason Swails <jason.swails@gmail.com> - 2013-07-23 08:39 -0400
                Re: Strange behaviour with os.linesep Vincent Vande Vyvre <vincent.vandevyvre@swing.be> - 2013-07-23 15:10 +0200
                Re: Strange behaviour with os.linesep Vincent Vande Vyvre <vincent.vandevyvre@swing.be> - 2013-07-23 15:26 +0200
                Re: Strange behaviour with os.linesep Jason Swails <jason.swails@gmail.com> - 2013-07-23 09:35 -0400
                Re: Simple Python script as SMTP server for outgoing e-mails? Chris Angelico <rosuav@gmail.com> - 2013-07-24 07:37 +1000
                Re: Simple Python script as SMTP server for outgoing e-mails? Chris Angelico <rosuav@gmail.com> - 2013-07-23 19:30 +1000
                [OT] SPF - was Re: Simple Python script as SMTP server for outgoing e-mails? Michael Torrie <torriem@gmail.com> - 2013-07-23 09:12 -0600
                Re: [OT] SPF - was Re: Simple Python script as SMTP server for outgoing e-mails? Chris Angelico <rosuav@gmail.com> - 2013-07-24 07:47 +1000
                non sequitur: [OT] SPF - was Re: Simple Python script as SMTP server for outgoing e-mails? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-07-23 19:59 -0400
                Re: non sequitur: [OT] SPF - was Re: Simple Python script as SMTP server for outgoing e-mails? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-24 01:42 +0000
                Re: Simple Python script as SMTP server for outgoing e-mails? Sanjay Arora <sanjay.k.arora@gmail.com> - 2013-08-05 18:43 +0530
                Re: Simple Python script as SMTP server for outgoing e-mails? Michael Torrie <torriem@gmail.com> - 2013-07-22 10:25 -0600
                Re: Simple Python script as SMTP server for outgoing e-mails? Chris Angelico <rosuav@gmail.com> - 2013-07-23 02:32 +1000
              Re: Simple Python script as SMTP server for outgoing e-mails? "Eric S. Johansson" <esj@harvee.org> - 2013-07-22 08:54 -0400
                Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-07-23 23:48 +0200
              Re: Simple Python script as SMTP server for outgoing e-mails? Michael Torrie <torriem@gmail.com> - 2013-07-22 08:10 -0600
                Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-07-23 23:50 +0200
  Re: Simple Python script as SMTP server for outgoing e-mails? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-07-21 12:39 -0400
  Re: Simple Python script as SMTP server for outgoing e-mails? Grant Edwards <invalid@invalid.invalid> - 2013-07-21 21:01 +0000
    Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-07-22 14:13 +0200
    Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-07-22 14:19 +0200
      Re: Simple Python script as SMTP server for outgoing e-mails? Grant Edwards <invalid@invalid.invalid> - 2013-07-22 14:10 +0000
      Re: Simple Python script as SMTP server for outgoing e-mails? Michael Torrie <torriem@gmail.com> - 2013-07-22 08:21 -0600
      Re: Simple Python script as SMTP server for outgoing e-mails? Chris Angelico <rosuav@gmail.com> - 2013-07-23 02:12 +1000
      Re: Simple Python script as SMTP server for outgoing e-mails? Nobody <nobody@nowhere.com> - 2013-07-22 21:32 +0100
  Re: Simple Python script as SMTP server for outgoing e-mails? Kevin Walzer <kw@codebykevin.com> - 2013-07-22 10:14 -0400
    Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-07-23 23:53 +0200
      Re: Simple Python script as SMTP server for outgoing e-mails? Kevin Walzer <kw@codebykevin.com> - 2013-07-24 10:38 -0400
        Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-08-01 16:15 +0200
          Re: Simple Python script as SMTP server for outgoing e-mails? Wayne Werner <wayne@waynewerner.com> - 2013-08-03 06:47 -0500
            Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-08-06 12:44 +0200
          Re: Simple Python script as SMTP server for outgoing e-mails? Kevin Walzer <kw@codebykevin.com> - 2013-08-03 21:41 -0400
            Re: Simple Python script as SMTP server for outgoing e-mails? Gilles <nospam@nospam.com> - 2013-08-06 12:45 +0200

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