smtp server blocks my ip only

N

natterjacks

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Apr 26, 2006
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Having a problem sending mails through my server since yesterday.
My ISP has tested with a temp account and it works fine for them from several different networks. I also tried the temp account and it failed once more.

The error I get in thunderbird is:

Sending of message failed.
The message could not be sent because connecting to SMTP server mail.myserver.com failed.

Seems the problem is only with my IP address and I can't work out why.
Have gone down the firewall route and there's nothing blocking my ip there. The files /etc/virtual/pophost and /etc/virtual/pophost_user contain my ip address and username (even after clearing the files and making another failed send attempt), so I am making a connection to the server and being blocked there somewhere.

All the blacklist files in /etc/virtual are empty, is there anything else I can check?

I'm running CentOS 4 with Exim 4.60

Thanks in advance for any tips!!
 
nope, the server must be blocking my IP.
I see my IP re-populate the pophost and pophost_user files after a failed smtp connection, so that proves that I'm getting through on port 25.
 
natterjacks said:
nope, the server must be blocking my IP.
I see my IP re-populate the pophost and pophost_user files after a failed smtp connection, so that proves that I'm getting through on port 25.
Click to expand...

SMTP connections don't populate the pophost files. That happens if a pop3 login occurs. Most ISP's block port 25, so I wouldn't doubt if yours does too. Try doing a "telnet $hostname 25" where $hostname is a valid server with an smtp daemon running that is not your ISP smtp server. If you get a prompt then your port is not blocked and you do have a problem with your server. If you just hang, then your ISP is blocking your port 25.
 
I did mention that I had gone down the firewall route, but I think I better clarify a little further.....

I connect to other smtp accounts from the same machine and am having no problems with those accounts. My ISP is not blocking port 25 and I have also confirmed with the hosting provider that they have no blocking in place for port 25.

of course pophost and pophost_user are for pop3 logins, don't know what I was thinking there (the "pop" should have given it away :rolleyes: )
 
Try doing to telnet to your server after doing a:
iptables --flush

If you just hang your server is not blocking your IP at all, it is being block somewhere else down the pipeline.

You said that you can use other smtp server from your computer, are they configured to use ssl? If so, that changes the port and normally the SSMTP port is not blocked by ISPs.
 
SMTP is not being blocked anywhere down the line.
The other SMTP Server that I use is from the same hosting company, in the same segment and is a virtual server configured exactly the same as the one giving me problems.

Telnet does hang when telneting to port 25 from my machine, but that doesn't always mean that the port is being blocked, only that there is no response back from the server.

This is why I think there's something blocking my ip on the server itself.
It wouldn't make sense that my ISP would block port 25 access from my IP and only to 1 specific machine.
 
Did you do the iptables --flush before doing the telnet? That is the only thing that would block an individual IP address to the server.
 
It's a virtual server and doesn't support iptables.

Any other suggestions are welcome!!
 
If you're not running a local firewall then you might want to check that your VPS provider's firewall isn't blocking it.

Can you do a traceroute (MS: tracert) to your server?

Can you ping your server?

Can you telnet to port 25?

When you do telnet to port 25 do you see any entries in /var/log/maillog? In /var/log/exim/mainlog? In /var/log/messages?

Is your IP# listed in /etc/hosts.deny?

Jeff
 
Thanks Jeff, but....
The provider assures me that they are not blocking my IP. This stopped working all of a sudden and I haven't made any changes to my firewall (double checked everything to make sure the problem wasn't local).
All other services are working fine, it's just SMTP to my server and from my IP that is causing the problem.
Telnet to port 25, like before, doesn't bring up the ESMTP banner like it should. After doing this again I checked the logging and my IP doesn't show.
My hosts.deny is also empty.
 
One thing that has bitten me in the arse too many times is spamassasin (and the SA area of exim.conf).

[No harm/insults/bad feelings intended to Jeff & others who have worked diligently over the years to assist with Exim/SpamBlocker]

We now comment out SA in exim.conf because SA - for some reason with us - rejects legitimate email (i.e., email that truly orginates from IBM, Lockheed Missles & Space, Paypal, eBay, etc.) and allows UCE to be delivered.

What the heck - it can't hurt - edit your exim.conf file & comment out the SA area, then restart exim.

Of course, this all rides on the fact that you're the admin of the box.

And hey, I've been wrong before......but it won't hurt your box.


Sloane
 
Thanks for the reply, I'll be giving that a go!!

I've worked around the problem for now by tunneling smtp through ssh. It would be nice to have a normal smtp server though ;)
 
no need to look, I've verified that it works fine from another IP address.
when I telnet to port 25 from my ip, the connection times out on me. When telneting from another ip to port 25 I get the esmtp banner as expected.

ip address (in case I missed something) is: 206.196.111.153

thanks for looking!!
 
Your IP# may be blocked somewhere. Or your ISP may be blocking port 25 off their network, as most do.

Jeff
 
Thanks, but:

natterjacks said:
I did mention that I had gone down the firewall route, but I think I better clarify a little further.....

I connect to other smtp accounts from the same machine and am having no problems with those accounts. My ISP is not blocking port 25 and I have also confirmed with the hosting provider that they have no blocking in place for port 25.

of course pophost and pophost_user are for pop3 logins, don't know what I was thinking there (the "pop" should have given it away :rolleyes: )
Click to expand...
 
quick Q in relation to this. Is there a quick way to limit which IPs SMTP will respond to? I only want a couple of IPs to be able to send emails through SMTP, block everyone else.
 
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