ISP blocking port 25 stops outgoing mail

[david.moss]

After half a day trying to get James to forward outgoing mail to the
Internet I was at my wits end. Everything seemed to be configured correctly,
James was accepting the message but it disappeared into a black hole.
Incoming mail worked fine. My existing mail account with the ISP worked
fine. It is always tempting to blame the new software in this situation, but
it wasn't the case.

 

My ISP, Telstra Bigpond, blocks port 25 for all but its own smtp server.
Apparently this is an anti-spam measure that you only find out about when
you try to run your own mail server. Most customers never encounter
limitation. Old discussion forums indicate that blocking port 25 for all but
the ISPs own service is quite common in the industry.

 

I've posted this article in the hope it may help save others the same
anxiety I felt when James failed to send outgoing e-mail.

 

The solution was to configure James to use the ISP's nntp server as a
gateway.  The James config file has a template that makes it easy:

 

<!-- A single mail server to deliver all outgoing messages. -->

            <!-- This is useful if this server is a backup or failover
machine, -->

            <!-- or if you want all messages to be routed through a
particular mail server, -->

            <!-- regardless of the email addresses specified in the message
-->

            <!-- -->

            <!-- The gateway element specifies the gateway SMTP server name.
-->

            <!-- If your gateway mail server is listening on a port other
than 25, -->

            <!-- you can set James to connect to it on that port using the
gatewayPort -->

            <!-- element. -->

            <!-- Although normally multiple addresses are implemented
through proper -->

            <!-- DNS configuration, the RemoteDelivery mail does allow
specifying -->

            <!-- multiple gateway elements, each of which may also have a
port -->

            <!-- e.g., mygateway:2525 -->

            <!-- the gatewayPort element is used as a default -->

           

            <gateway>mail.bigpond.com</gateway>

            <gatewayPort>25</gatewayPort>

         

            <!-- If the gateway requires smtp authentication the following
directives -->

            <!-- (gatewayusername/gatewayPassword) can be used. -->

           

            <gatewayusername>your_username</gatewayusername>

            <gatewayPassword>your_password</gatewayPassword>

 

David Moss

 

 

[Al Stu]

No, blocking port 25 for external SMTP mail servers is not standard.  In
fact it would inhibit the use of services such as Google Apps mail / GMail
and many other external mail services that provide POP/SMTP capability.

Is there a possibility you are misinterpreting what is actually blocked?

For instance many ISP's register their dynamic IP addresses that are
assigned to customers with services such as SPAMHaus Policy Block List (PBL
http://www.spamhaus.org/pbl/index.lasso) as not being permitted to send mail
directly.  This means if you send a message to say Someone@...
through your locally hosted James SMTP server, Comcast will look up the
address of your mail server and see that your ISP has PBL'd it and thus the
Comcast mail server will reject the message.

Perhaps your ISP really is blocking port 25 as you say, but the above is far
more likely scenario.  But as you have discovered, the work around is to use
your ISP's SMTP server just as you would for an email client such as Outlook
Express, etc.

Or you could host your mail server externally some place where you have
control of IP address registering etc.  Such as here:
https://www.rapidvps.com/?vps=14265




----- Original Message -----
From: "david.moss" <david.moss@...>
To: <server-user@...>
Sent: Sunday, June 29, 2008 8:02 PM
Subject: ISP blocking port 25 stops outgoing mail


After half a day trying to get James to forward outgoing mail to the
Internet I was at my wits end. Everything seemed to be configured correctly,
James was accepting the message but it disappeared into a black hole.
Incoming mail worked fine. My existing mail account with the ISP worked
fine. It is always tempting to blame the new software in this situation, but
it wasn't the case.



My ISP, Telstra Bigpond, blocks port 25 for all but its own smtp server.
Apparently this is an anti-spam measure that you only find out about when
you try to run your own mail server. Most customers never encounter
limitation. Old discussion forums indicate that blocking port 25 for all but
the ISPs own service is quite common in the industry.



I've posted this article in the hope it may help save others the same
anxiety I felt when James failed to send outgoing e-mail.



The solution was to configure James to use the ISP's nntp server as a
gateway.  The James config file has a template that makes it easy:



<!-- A single mail server to deliver all outgoing messages. -->

            <!-- This is useful if this server is a backup or failover
machine, -->

            <!-- or if you want all messages to be routed through a
particular mail server, -->

            <!-- regardless of the email addresses specified in the message
-->

            <!-- -->

            <!-- The gateway element specifies the gateway SMTP server name.
-->

            <!-- If your gateway mail server is listening on a port other
than 25, -->

            <!-- you can set James to connect to it on that port using the
gatewayPort -->

            <!-- element. -->

            <!-- Although normally multiple addresses are implemented
through proper -->

            <!-- DNS configuration, the RemoteDelivery mail does allow
specifying -->

            <!-- multiple gateway elements, each of which may also have a
port -->

            <!-- e.g., mygateway:2525 -->

            <!-- the gatewayPort element is used as a default -->



            <gateway>mail.bigpond.com</gateway>

            <gatewayPort>25</gatewayPort>



            <!-- If the gateway requires smtp authentication the following
directives -->

            <!-- (gatewayusername/gatewayPassword) can be used. -->



            <gatewayusername>your_username</gatewayusername>

            <gatewayPassword>your_password</gatewayPassword>



David Moss







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[Ben Dinnerville]

What David is describing is correct.

Telstra / Bigpond block all traffic on the network to port 25 except  
where the traffic is to / from their own smtp servers. They do this  
for both business and residential customers.

I know this because we provide mail hosting services to a couple of  
small businesses that use Telstra and Telstra did no notify anyone  
when they implemented this change - they just blocked it without  
notification - you can imagine the headaches it provided for  
businesses that were using our mail server for their hosted mail - one  
day they could send mail, the next they couldnt with no explanation.  
After many hours on the phone trying to get an answer from Telstra (as  
well as a lot of other head scratching) we found out that they block  
connection to 25 - with spam being the reason they do it.

Whilst they do block you from connecting to external mail servers,  
they do run their mail servers as an open relay for anyone on their  
network, meaning you can still send and receive mail using your own  
domain names (including gmail etc) - you lose the storing of sent mail  
on services such as gmail thou.

I think (am not sure thou) that they only block 25, you can still  
connect to smtp servers on other ports over 1024 if you can get a mail  
server reconfigured to accept connections on these ports and also  
configure your mail clients / mta's to connect to to a port other than  
25.

Cheers,

Ben


On 30/06/2008, at 1:32 PM, Al Stu wrote:

No, blocking port 25 for external SMTP mail servers is not standard.  In
fact it would inhibit the use of services such as Google Apps mail /  
GMail
and many other external mail services that provide POP/SMTP capability.

Is there a possibility you are misinterpreting what is actually blocked?

For instance many ISP's register their dynamic IP addresses that are
assigned to customers with services such as SPAMHaus Policy Block List  
(PBL
http://www.spamhaus.org/pbl/index.lasso) as not being permitted to  
send mail
directly.  This means if you send a message to say Someone@...
through your locally hosted James SMTP server, Comcast will look up the
address of your mail server and see that your ISP has PBL'd it and  
thus the
Comcast mail server will reject the message.

Perhaps your ISP really is blocking port 25 as you say, but the above  
is far
more likely scenario.  But as you have discovered, the work around is  
to use
your ISP's SMTP server just as you would for an email client such as  
Outlook
Express, etc.

Or you could host your mail server externally some place where you have
control of IP address registering etc.  Such as here:
https://www.rapidvps.com/?vps=14265




----- Original Message -----
From: "david.moss" <david.moss@...>
To: <server-user@...>
Sent: Sunday, June 29, 2008 8:02 PM
Subject: ISP blocking port 25 stops outgoing mail


After half a day trying to get James to forward outgoing mail to the
Internet I was at my wits end. Everything seemed to be configured  
correctly,
James was accepting the message but it disappeared into a black hole.
Incoming mail worked fine. My existing mail account with the ISP worked
fine. It is always tempting to blame the new software in this  
situation, but
it wasn't the case.



My ISP, Telstra Bigpond, blocks port 25 for all but its own smtp server.
Apparently this is an anti-spam measure that you only find out about  
when
you try to run your own mail server. Most customers never encounter
limitation. Old discussion forums indicate that blocking port 25 for  
all but
the ISPs own service is quite common in the industry.



I've posted this article in the hope it may help save others the same
anxiety I felt when James failed to send outgoing e-mail.



The solution was to configure James to use the ISP's nntp server as a
gateway.  The James config file has a template that makes it easy:



<!-- A single mail server to deliver all outgoing messages. -->

            <!-- This is useful if this server is a backup or failover
machine, -->

            <!-- or if you want all messages to be routed through a
particular mail server, -->

            <!-- regardless of the email addresses specified in the  
message
-->

            <!-- -->

            <!-- The gateway element specifies the gateway SMTP server  
name.
-->

            <!-- If your gateway mail server is listening on a port  
other
than 25, -->

            <!-- you can set James to connect to it on that port using  
the
gatewayPort -->

            <!-- element. -->

            <!-- Although normally multiple addresses are implemented
through proper -->

            <!-- DNS configuration, the RemoteDelivery mail does allow
specifying -->

            <!-- multiple gateway elements, each of which may also  
have a
port -->

            <!-- e.g., mygateway:2525 -->

            <!-- the gatewayPort element is used as a default -->



            <gateway>mail.bigpond.com</gateway>

            <gatewayPort>25</gatewayPort>



            <!-- If the gateway requires smtp authentication the  
following
directives -->

            <!-- (gatewayusername/gatewayPassword) can be used. -->



            <gatewayusername>your_username</gatewayusername>

            <gatewayPassword>your_password</gatewayPassword>



David Moss







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[JAMES Nightly Build System]

> My ISP, Telstra Bigpond, blocks port 25 for all but its own smtp server.
> Apparently this is an anti-spam measure

Yes, I wish that all ISPs would do this port blocking, at least for consumer
accounts in DHCP pools, and force the ISPs to do SPAM filtering on their end
before it hits the Internet.

        --- Noel



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