How to tell if my ISP block port 25?

jme · 05-17-2004, 08:30 AM

How can I tell if my ISP blocks port 25 connections?

What is the best way of going about this as I have just setup a mail server using the www.qmailrocks.org tutorial and all seems to be working well internally, but I cannot accept any emails from external sources.

I have configured my smoothwall router to forward all port 25 requests to the correct macine, and surfing to http://mail.mydomain.com shows my webmail interface so why can I not get the emails from the external sources?

Any suggestions would be welcome.

Cheers Guys,
Jamie

GraemeK · 05-17-2004, 08:52 AM

mine do that until you prove your not an open relay!

Look on your ISP's website or ask them! they'll probably be able to test it over the phone and enable port 25 there and then.

G

davholla · 05-17-2004, 08:55 AM

www.grc.com scans your ports to see if they are open.

leckie · 05-17-2004, 09:01 AM

to find all blocked ports scan your ip address from an external host with nmap.

nmap <ip addy>

all ports blocked come up with the key word "filtered"

LuggerHouse · 05-17-2004, 09:02 AM

What I do is stop mail services, setup telent server in xinetd.d to listen to 25. Then from external I telnet my server on 25.

This way I can certify if it's blocked or not...

onnyloh · 05-17-2004, 09:06 AM

use this online port verifyer
hope this may help
http://www.blackcode.com/net-tools/

jme · 05-17-2004, 10:00 AM

Thanks all for your help and responses.

Quote:

Originally posted by davholla
www.grc.com scans your ports to see if they are open.

This one worked a charm, but found that my port 25 was blocked so I think that some gentle crawling to my ISP should be able to get them to open the port up for me.

Cheers guys,
Jamie

LuggerHouse · 05-17-2004, 10:09 AM

Quote:

Originally posted by jme
Thanks all for your help and responses.

This one worked a charm, but found that my port 25 was blocked so I think that some gentle crawling to my ISP should be able to get them to open the port up for me.

Cheers guys,
Jamie

If you're not lucky, just like me, and your ISP will not unblock you port 25, there is another low cost alternative:

have a look at no-ip.com

They offer to redirect you mail to another port on your machine... You just specify no-ip as your mail manager (MX record in DNS) and they will receive the mail and redirect it on another port...

Works great, it's my set-up and it's handling about 100 mail per day..

jme · 05-30-2004, 01:00 PM

Quote:

Originally posted by LuggerHouse
If you're not lucky, just like me, and your ISP will not unblock you port 25, there is another low cost alternative:

have a look at no-ip.com

They offer to redirect you mail to another port on your machine... You just specify no-ip as your mail manager (MX record in DNS) and they will receive the mail and redirect it on another port...

Works great, it's my set-up and it's handling about 100 mail per day..

Well I have had to go the no-ip route and get the forwarding service, but I am having problmes getting qmail to 'listen' to a different port other than 25.

Any suggestions?

Jamie

zaphodiv · 05-30-2004, 03:27 PM

A quick google for how to change the port in qmail finds this link (scroll down) which might be helpfull.

Alternativly you could leave portfwd running to tunnel connections from the alternative port to port 25.