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Niceman2005 05-10-2006 08:35 PM

Dear friends,

One of our users tried to use his PDA to access mail from our mail server. BUt for some reason, when he tried to send mail, it says ""CLIENT HOST BLOCKED USING"

Anyone has any idea what is wrong? Is this relay thingi the one about blocking spam?

thanks for taking time helping,


gilead 05-10-2006 10:17 PM

It sounds like your mail server is using one of the realtime blackhole lists to limit the boxes that can send mail. Have you checked the config of your mail server?

Niceman2005 05-11-2006 12:45 AM

Hi gilead,

Thanks for your reply. The problem only happen with one user and he is using PDA to send. Everything works fine from a normal computer.

The guy use this GPRS internet supplied by a telecommunication company. he tried to configure his mail client software to use our company mail server and then tried again with the ISP mail server. Both couldn't allow him to send mail but both allow him to receive mails. Its weird.....

It is unlikely the blackhole list is blocking my company mail server because that is ok whn send from other our home or ffrom our company. The only possiblity is that the external address supplied by the GPRS ISP has been blocked by the blackhole list.....
maybe the external mail address supplied by the GPRS ISP got something wrong....I also not sure..

gilead 05-11-2006 02:12 PM


Originally Posted by Niceman2005
The only possiblity is that the external address supplied by the GPRS ISP has been blocked by the blackhole list

That sounds like what is happening - are you using sendmail? I'm not sure if the allow list (access db) overrides the deny list, but you may be able to add the IP address range he gets to your access db so he can send.

Niceman2005 05-17-2006 09:52 PM

Hi Gilead..

thanks for your help. I just figured out the problem. Yes you are right, the sender's mail server is in the list under &

I am using postfix, so I commented the two list, by doing that it enables all the previously blocked mails to come in.

However, isn't that a crappy solution? since I added those list initially to make use of the database to block spam mails, now i have to uncomment it just because one of the mail server blacklisted there is unable to send to my mail server.

It seems to me the and has wrongly blocked the address.

Hope anyone can help me...

gilead 05-17-2006 10:06 PM

You're right - if you have a use for the and services then turning them off for one user isn't practical.

What errors does he get when trying to use his ISP's mail server? It would be better to get that working if possible.

Niceman2005 05-17-2006 10:11 PM

Hi Gilead,

Here are the initial errors:

Reason: Service unavailable; Client host [] blocked
using; This mail was handled by an open relay - please
visit <>

and another one:
Reason: Service unavailable; Client host [] blocked using;

The two errors has been solved after I removed the use of and


gilead 05-17-2006 10:52 PM

Does he have his own ISP though? If he does and gets an error sending mail through them, is it the same error? If it's a different error it may be easier to resolve that so he's not sending mail through your server which means you can leave the ordb rules in place.

Niceman2005 05-18-2006 12:59 AM

Hi Gilead,

Yes, he is using his own ISP to send mail to our company server. So it means his ISP address was blacklisted by the database.

thanks !


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