Web Hosting Talk : Web Hosting Main Forums : Running a Web Hosting Business : ISPs blocking webhosting customers from using SMTP.

[Host Ultra]

Does anyone have a list of the ISP's that block their customers from using SMTP servers?

The amount of people complaining to me that their SMTP suddenly stopped working has increased in the past few weeks.
It has always turned out that their ISP, without any warning disabled their customers from using any SMTP server exept their own.

This is impossible for me to tell from my end if its their ISP.
All i see is the customers mail account on our server works perfectly, but how to explain to the customer that its not our problem?

[consul]

Hmmm... We might be experiencing the same problem. I have to check with that ISP of our client.

Thank you very much for this question.

[dynamicnet]

Greetings:

"Does anyone have a list of the ISP's that block their customers from using SMTP servers?"

Yes, there are a number of ISP's that use this procedure (no, we don't have a list).

Thank you.

[BP Steven]

For anyone suffering from this you should run a copy of your SMTP server on port 26 so clients can get around the blocks. If you're using cPanel you can set it up from WHM.

[rewobo]

With my current ISP they have blocked the port 25.

[Moriarty]

My ISP redirects outgoing connections to port 25 to their own SMTP server. This is even worse than just blocking access to other mail servers as you can think you are connecting to one server and really be using theirs. This is obviously a problem if the server you _think_ you are connecting to uses SMTP AUTH.

[datums]

I know that Cox Communication has disabled port 25. You can't even connect to their own mail server. Their cable isp service offers 7 email accounts, I don't what they are doing to fix this. I know they told a customer to upgrade to a business account. Changing the port smtp listens on will not work, someone sending mail to one of your customers will not know that you have changed the standard port.


http://computer.howstuffworks.com/email5.htm

[UmBillyCord]

Why is it a problem to just change the outgoing mail server to the customers ISPs? MSN and a few others have been doing this for over a year now. We just have the cusotmer use their ISP SMTP server name. In fact we like it when customers use their ISPs SMTP server over ours.

[The Prohacker]

Originally posted by datums
Changing the port smtp listens on will not work, someone sending mail to one of your customers will not know that you have changed the standard port.

You of course leave 25 open but you also wrap another port such as 2525 or 26 to 25 to get around this... Iptables is great for this

[0utlier]

Not sure if this is a dumb question or not, but what about sending email via the PHP mail function. Is it blocked?

[CSD_Hosting]

I just set Exim to run 2 copies of itself, one on port 26, and one on port 25, its working just fine

Outliner: correct me if im wrong, but i think mail() uses the SMTP server, so you can send it, but ISP are blocking it from home computers, mail() uses the servers SMTP service, so unless someone wants to send all of their mail from a website, that wont work, The error is client side, not server side

[Hey It's Me]

In fact we like it when customers use their ISPs SMTP server over ours.

So do we. Some of our most taxing issues have been mail related.

[H2]

ATT WorldNet
Earthlink
MSN
Mindspring
Sympatico
Cox.net (one week ago)

Let me know if I am wrong.

[GideonX]

add RCN to that list...

[visionsless]

COX CABLE is the biggest piece of crap and they just started blocking us users from using port 25 because of spame reasons