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Reverse DNS?

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6 replies

by phingers 1 view

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I have received a message from somebody saying the following:

Your first MX record is invalid:

http://www.samspade.org/t/lookat?a=greencell.co.uk

(remove spaces from the url)

mail.greencell.co.uk [213.208.89.218 ] is not functioning.

Our mail server is working on this IP address. I followed the link to samspade but can't see what the problem is. Any ideas? It suggests that there is no reverse DNS, do I need it and how do I set it up if I do?

6 replies

by curlergirl

I checked your IP and reverse DNS is not working for your mail server address. Some email systems can be set to require a valid PTR record (reverse DNS lookup) before they will accept the email. If this is what is causing the problem in your case,you need to contact your ISP and ask them to set up a PTR record for your mail server. Hope this helps!

by curlergirl

PS - this is presuming your ISP has the authoritative DNS records for your domain. This is the way it looked to me when I did a lookup on your domain name.

by joseph moore

Actually, I think the problem lies on your server. When I did a NSLOOKUP on my DNS server for your domain, I get the following:

Non-authoritative answer:
greencell.co.uk MX preference = 40, mail exchanger = blackmail.nildram.co.uk
greencell.co.uk MX preference = 10, mail exchanger = mail.greencell.co.uk
greencell.co.uk MX preference = 20, mail exchanger = whitemail.nildram.co.uk
greencell.co.uk MX preference = 30, mail exchanger = mailq.nildram.co.uk

greencell.co.uk nameserver = dns01.techgate.co.uk
greencell.co.uk nameserver = dns02.techgate.co.uk
mail.greencell.co.uk internet address = 213.208.89.218
dns01.techgate.co.uk internet address = 217.161.12.176
dns02.techgate.co.uk internet address = 217.161.12.175

Then, when I did a DNS query on your server (at 213.208.89.218) I got the following:

> greencell.co.uk
Server: [213.208.89.218]
Address: 213.208.89.218

greencell.co.uk
primary name server = gc2kdar.greencell.co.uk
responsiblemail addr = admin
serial = 4921
refresh = 900 (15 mins)
retry = 600 (10 mins)
expire = 86400 (1 day)
default TTL = 900 (15 mins)

The important line here is the "primary name server", which points to gc2kdar.greencell.co.uk

And I think that that is the problem. You cannot resolve "gc2kdar.greencell.co.uk" with an IP address. If you try, you get a Host Does Not Exist error.

And if the primary name server for your domain can't be found, then how am I gonna resolve mail.greencell.co.uk?

So, I suggest you check at the gc2kdar.greencell.co.uk first. Contact your ISP (techgate.co.uk) and make sure they are ok. Then check out your own DNS and make sure it is ok. I think you will find theproblem at the ISP, personally!

Now, I am not the best at DNS (it is really complicated, IMHO), but this is what I am seeing.

hope this helps

by phingers

Thanks. My ISP still maintains there is nothing wrong and mail is being sent and delivered from the mail server. I'm still not convinced they're just slacking with the DNS and need to enter a reverse lookup, either that or I do on the mail server! Anyway, have some points for your thorough answer

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