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

From Grant Edwards <invalid@invalid.invalid>
Newsgroups comp.lang.python
Subject Re: Simple Python script as SMTP server for outgoing e-mails?
Date 2013-07-22 14:10 +0000
Organization PANIX Public Access Internet and UNIX, NYC
Message-ID <ksjefo$krt$1@reader2.panix.com> (permalink)
References <gksnu85fe69utl50s4e1tik0bhinndls3m@4ax.com> <kshi6l$lvc$1@reader2.panix.com> <tp8qu81vrhft7o89dp9551ju49t2i0a5nv@4ax.com>

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On 2013-07-22, Gilles <nospam@nospam.com> 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. ?

There are a variety of things they check.  They've got lists of IP
address blocks that they know are residential DSL/cable customers, and
sometimes they'll reject mail from those regardless of what you do.

Some will compare the reverse-DNS lookup with the headers to make sure
you're being honest about things like return-path, some will compare
the IP address with the MX record for the domain they got when they
did the reverse-lookup-DNS, and they've all probably got a variety of
other secret heuristics they use to generate a "SPAM" score.

For many years I ran my own SMTP server and had it configured to
deliver mail directly to recipients.  About 10 years, I had to give up
on that because so many SMTP servers were rejecting/ignoring mail I
sent.  And I did have a static IP with a valid domain and MX record.

But it was a residential DSL IP address, and I suspect that was enough
to get mail rejected by some servers.

-- 
Grant Edwards               grant.b.edwards        Yow! Well, O.K.
                                  at               I'll compromise with my
                              gmail.com            principles because of
                                                   EXISTENTIAL DESPAIR!

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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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