Question

petkoa  |   Jan 29 2007  6:23AM GMT

Hi maryam82,

If you have no trouble receiving mail from other people/networks, then the problem is hardly related to your DNS server configuration. Your correspondent also had problems reaching hotmail.com servers, though log in this case is very scarce…

May be your correspondent have transient (ISP/backbone/etc related) problems reaching DNS servers on the internet, or have some problems with own resolver - e.g. dropping UDP packets on the firewall? The latter could happen on a stateful firewall because of long timeouts which lead to expiration of the expectation for the UDP “connection” (yes, UDP is connectionless, but stateful packet inspection on the firewall treats it in a manner similar to TCP connections)

BR,

Petko

PDMeat  |   Jan 29 2007  10:05AM GMT

It sounds like his mail server is complaining that when it looks up your email domain for MXs, it finds none. This can best be troubleshot using <a href="http://www.dnsstuff.com" rel="nofollow">www.dnsstuff.com</a> and look up your domain for MX records. Also, make sure that you have valid PTR records for all A records (and only ONE PTR per A record is allowed in SMTP) of your email host MXs. If you don’t have a valid PTR and A record to back up your MX, many email servers will refuse your message and you should get an NDR to that effect, though not in every case.

If you are having problems sending email from your co to hotmail, it’s liekly there is a problem with something in your MX, A or PTR records for email. Keep in mind that many large organizations particulalrly, Hotmail, AOL, etc have their own Blacklists and they don’t necessarily care what the public RBL’s say about you. It’s quite possible that, for exmaple, if you have a wrong or no PTR record for your MX/A record, hotmail will blacklist you without warning and you may not show up in any public RBL.

If you know how to telnet into a mail server on port 25 from your mail server, you’ll see the error’s show up in the telnet session usually. There should be an error in your UNIX (sendmail?) SMTP logs if your logging level is on and working properly.

Good luck.

maryam82  |   Jan 30 2007  1:19AM GMT

Dear All,
Thank You for all your replies.

Our email server can not be pinged from outside because of the firewall settings. Only SMTP and POP3 are allowed. Using <a href="http://www.dnsstuff.com," rel="nofollow">www.dnsstuff.com,</a> I noticed that we do not have PTR records. But if this issue maybe causing a problem shouldn?t other companies face the same problem when sending us emails not a particular company? Our Institute has no problem sending to hotmail, it is the other company. After several attempts from his side I received the emails he is sending on my Institute account. Also he is facing problems receiving from us therefore I send emails to his hotmail account. It is more likely as you said, Petkoa, ISP problems, we both are on different ISPs. The problem still exsists. It is just that no changes where made on both sides, previously no problems occured.
Thanks in advance for your help.

bermuda  |   Jan 30 2007  8:30AM GMT

The DNS server that your correspondent is trying to use to resolve your smtp/domain name is 195.226.240.60 which is in Kuwait. I don’t know where you or your correspondent are based - is Kuwait halfway round the world ?
The reason I ask is two-fold… it’s possible your correspondents configured gateway for his outmail is sending you on a wild goose-chase (ie not using the shortest route for next hop to his ISPs DNS server (which is obviously likely to be very close to where his system is).
It is vaguely possible that the Kuwaiti DNS server has not updated properly / anyway has the wrong IP address (if any) for you. It may not effect any other mail he sends to anyone else.
On a slightly different tack…
Is the DNS setting he uses actually set at his mail server or is it derived from the gateway his server connects to?
Not very helpful but check if going via Kuwait is anything like a short(-ish) route.

maryam82  |   Jan 31 2007  2:20AM GMT

Hi all,

Well we are both located in Kuwait. and the DNS (195.226.240.60) belongs to his ISP Qualitynet. I will contact him and check how his network settings are?

Further more, i asked him to send me an email from his account to my Institute account. The email he sent is queued in a “remote queue”, also other emails are queue in different queues. But only the email sent to me was queued in that particular queue. Does that indicate that his mail server is having problems connecting to our mail server or is it a general network problem, for example he needs to check his cable, IP settings, etc? Also, strangely before that happened i received emails from him and when i asked him to try again the queue problem occured. He has no problem receiving from us on his mail server, at the time my mail were queue i sent him and he immediately received them.