Who is blocking my smtp connection

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Newsgroups:  comp.os.linux.networking
Date:        Sun, 23 Oct 2005 20:21:24 -0400

Who is blocking my smtp connection

> I get "connection time out" error to all the major email sites' smtp port.
> E.g.,
>
> telnet mx4.mail.yahoo.com smtp
> telnet mx2.mail.yahoo.com smtp
>
> or hotmail/gmail.

'tcptraceroute' will let you do a traceoute using a specified TCP port (like port 25 for SMTP). This will tell you what server/router is blocking the connections.

Paul Colquhoun

Who is blocking my smtp connection

> I'm suspecting that my ISP is blocking all its clients' smtp
> connection. How can I prove that?

Read your TOS (Terms of Service) to see if it prohibits you from operating any specific services such as a web site or SMTP MTA (Mail Transport Agent), then use " tcptraceroute mx4.mail.yahoo.com 25 " or some such to see where the traffic gets blocked. Most likely it will be at an address within your ISP's control.

ynotssor

Who is blocking my smtp connection

$ tcptraceroute mx3.mail.yahoo.com 25
Selected device eth0, address 69.197.185.118, port 36144 for outgoing packets
Tracing the path to mx3.mail.yahoo.com (64.156.215.8) on TCP port 25 (smtp), 30 hops max
 1  * * *
 2  * * *

$ tcptraceroute mx3.mail.yahoo.com 587
Tracing the path to mx3.mail.yahoo.com (64.156.215.6) on TCP port 587 (submission), 30 hops max
 1  10.90.208.1  55.064 ms  71.303 ms  76.547 ms
 2  gw03.ym.phub.net.cable.rogers.com (66.185.90.17)  77.996 ms  87.208 ms  78.465 ms
10  UNKNOWN-66-218-82-223.yahoo.com (66.218.82.223)  94.844 ms  177.826 ms  137.046 ms
11  mta-v21.level3.mail.yahoo.com (64.156.215.6) [closed]  119.104 ms  187.711 ms  203.776 ms

$ tcptraceroute smtp.broadband.rogers.com 25
10  t-3-1.bas2.re2.yahoo.com (206.190.33.95)  124.000 ms  170.838 ms  158.735 ms
11  smtp2.rog.mail.vip.re2.yahoo.com (206.190.36.18) [open]  58.968 ms  78.767 ms  141.179 ms

Who is blocking my smtp connection

> telnet mx4.mail.yahoo.com smtp
> or hotmail/gmail.

well, for gmail, try this … (edited for brevity)

# openssl s_client -connect smtp.gmail.com:465

CONNECTED(00000003)
depth=0 /C=US/ST=California/L=Mountain View/O=Google
Inc/CN=smtp.gmail.com
---
Certificate chain
 0 s:/C=US/ST=California/L=Mountain View/O=Google Inc/CN=smtp.gmail.com
---
Server certificate
-----BEGIN CERTIFICATE-----
-----
New, TLSv1/SSLv3, Cipher is DES-CBC3-SHA
Server public key is 2048 bit
SSL-Session:
    Protocol  : TLSv1
    Cipher    : DES-CBC3-SHA
    Session-ID:
6597C02593BEA13BC4A3EA0CF692E5803034FAD080C6287332D4986DB8B0B20E
Session-ID-ctx:
    Master-Key:
F2E23E906DA0C693625AB52AD40A66649FAFC4C6F11B3819E6561390B0BFBA16091A9E58D5F80D8BAC398EFCE48896E7
    Key-Arg   : None
    Start Time: 1100699679
    Timeout   : 300 (sec)
    Verify return code: 21 (unable to verify the first certificate)
---
220 smtp.gmail.com ESMTP v71sm1679cwb
EHLO slackserv
250-smtp.gmail.com at your service

Raqueeb Hassan

Who is blocking my smtp connection

> I'm suspecting that my ISP is blocking all its clients' smtp connection.

Many ISPs are blocking off net SMTP servers, to reduce spam. Some ISPs provide another port that can be used or secure access.

James Knott

Who is blocking my smtp connection

Rogers block outgoing port 25 traffic: http://www.digitalhomecanada.com/forum/archive/index.php/t-26854.html

Reconfigure your SMTP server to relay through Rogers' SMTP (aka smarthost).

Snowbat