No Inbound Email

[speedracercjr]

Ok this was weird. For about 15 minutes all inbound email was bouncing. Internally E2K was running fine, we could also send out, just couldn't recieve. I don't know much about MX records and all, but is it possible the server that the MX record is stored on had a problem which then meant that no one could find our location on the net? Inbound email is now functioning again and some email's that didn't bounce finally arrived.

 

[mleggatt]

Usually when an SMTP server attempts to send an email to your domain it looks up the MX record for your domains mail server to find the IP address of your public mail server. If this SMTP's DNS server does not have your domains MX record cached(i.e. it has looked it up recently) then it will attempt to contact your ISP's DNS server to get the MX (mail exchanger) IP address. If your ISP's DNS is down then when the remote SMTP server tries to send the email it will not be able to find your mail servers IP address and the email will fail to be delivered. Most if not all ISP's tend to have at least two DNS serverss so if one fails the other is still available. If you have your ISP's DNS server addresses you can check several things:


1. Are their DNS servers available, if you have the IP address of their DNS servers (they should have this on their support site, or they will let you know if you call them) you can try pinging these servers. (assuming you have internet access)

2. Is the MX record available by using nslookup from the command line.

Open a command line

type nslookup

at ">" prompt type "set query=mx" to set the query type to mail exchanger.

then "Server=dns.abc.com" replace dns.abc.com with your ISP's DNS server so that the query will query your ISP's DNS server.

then type your domain name at the ">" prompt

It should return something like:

> axsone.com
Server: dns.abc.com
Address: 194.119.131.65

Non-authoritative answer:
abc.co.uk MX preference = 50, m
abc2.co.uk MX preference = 50, m
abc3.co.uk MX preference = 10, m

abc.co.uk nameserver = ns1.demon.co.uk
abc.co.uk nameserver = ns2.demon.net
abc.co.uk nameserver = ns0.demon.co.uk
mail-1.mail.isp.net internet address = 123.123.123
mail-1.mail.isp.net internet address = 123.123.124
mail-2.mail.isp.net internet address = 123.123.125
mail-2.mail.isp.net internet address = 123.123.126
ns0.isp.co.uk internet address = 121.121.1.60
ns1.isp.co.uk internet address = 121.121.1.61
ns2.isp.net internet address = 209.124.125.110

If all emails are bouncing to your domain either:

1. Other mail servers cannot access your mail servers IP address. Test this by pinging your mail servers public IP externally.

2. Other mail servers cannot resolve your MX mail exchanger record on your ISP DNS servers (or yours if you host your own DNS).

3. The E2K server is bouncing messages because of misconfiguation or a fault.

You can diagnose the issue more if you get a copy of the bounce messages external users are getting. It is worth having a web enabled external email account (On an external ISP) that you can either get external users to send the bounce messages to or you can send a message from to your internal account and see what the bounce error is for yourself.

 

[mleggatt]

Usually when an SMTP server attempts to send an email to your domain it looks up the MX record for your domains mail server to find the IP address of your public mail server. If this SMTP's DNS server does not have your domains MX record cached(i.e. it has looked it up recently) then it will attempt to contact your ISP's DNS server to get the MX (mail exchanger) IP address. If your ISP's DNS is down then when the remote SMTP server tries to send the email it will not be able to find your mail servers IP address and the email will fail to be delivered. Most if not all ISP's tend to have at least two DNS serverss so if one fails the other is still available. If you have your ISP's DNS server addresses you can check several things:


1. Are their DNS servers available, if you have the IP address of their DNS servers (they should have this on their support site, or they will let you know if you call them) you can try pinging these servers. (assuming you have internet access)

2. Is the MX record available by using nslookup from the command line.

Open a command line

type nslookup

at ">" prompt type "set query=mx" to set the query type to mail exchanger.

then "Server=dns.abc.com" replace dns.abc.com with your ISP's DNS server so that the query will query your ISP's DNS server.

then type your domain name at the ">" prompt

It should return something like:

> axsone.com
Server: dns.abc.com
Address: 123.123.132.44

Non-authoritative answer:
abc.co.uk MX preference = 50, m
abc2.co.uk MX preference = 50, m
abc3.co.uk MX preference = 10, m

abc.co.uk nameserver = ns1.isp.co.uk
abc.co.uk nameserver = ns2.isp.net
abc.co.uk nameserver = ns0.isp.co.uk
mail-1.mail.isp.net internet address = 123.123.123
mail-1.mail.isp.net internet address = 123.123.124
mail-2.mail.isp.net internet address = 123.123.125
mail-2.mail.isp.net internet address = 123.123.126
ns0.isp.co.uk internet address = 121.121.1.60
ns1.isp.co.uk internet address = 121.121.1.61
ns2.isp.net internet address = 209.124.125.110

If all emails are bouncing to your domain either:

1. Other mail servers cannot access your mail servers IP address. Test this by pinging your mail servers public IP externally.

2. Other mail servers cannot resolve your MX mail exchanger record on your ISP DNS servers (or yours if you host your own DNS).

3. The E2K server is bouncing messages because of misconfiguation or a fault.

You can diagnose the issue more if you get a copy of the bounce messages external users are getting. It is worth having a web enabled external email account (On an external ISP) that you can either get external users to send the bounce messages to or you can send a message from to your internal account and see what the bounce error is for yourself.

 

[speedracercjr]

Yeah I did the MX lookup and it all looks fine. I didn't get to try it when we were "down". Also the emails i sent from Hotmail never bounced, they just waited until everything was working again and finally made it through. I've asked one of the users to get their friend to send me the NDR they got yesterday so we'll see what that says.

 

[kse]

I have the same problem I can send out but if I send from hotmail account I do not recieveit, it bounced, speedracercjr what did you do to made it through?

Thanks

 

[mleggatt]

Guys,

If you have problems getting email from one particular provider/ISP i.e. hotmail it maybe worth checking with your ISP that they are not using some sort of Anti-spam system that is blocking legitimate emails and that the legitimate senders address is not originating from an email server that is on a realtime blacklist like

http://www.orbl.org.

It maybe of use to you to use software called SamSpade

http://www.samspade.org/

which allows you to do lots of command line type commands from a single interface i.e. ping, nslookup, whois, traceroute.

Hope this helps you.

 

[kse]

I have checked with my ISP they said the problem is from my side, how can I solve it? help!!!!!!!!!!!

 

[mleggatt]

First, don't always take someone else word for it that a fault is caused on your end of a shared system, it's best to verify this for yourself (knowledge/experience allowing). If your ISP suggests that the fault is on your end ask them if they know what the fault is and what leads them to believe the fault is on your end. In order to help I have a few questions:

1. Have you got a copy of the messages that bounced along with the non-delivery report? Often these messages give you an indication of why the email failed.

2. I think you are receiving email via SMTP from your ISP. i.e. your ISP just forwards all email for your domain through to your mail server. YOu can also pull email into mail boxes via POP3 from your ISP's mail server.

3. Have you looked at the log files on your mail server for errors?

4. Is it just messages that originate from hotmail that is the problem?

Just for info when you send an email normally the mail passes from mail server to mail server but if there is a problem with one of the mail servers on route i.e. it is not available the final mail server before the problem one will keep attempting to send the email on until either the timeout period is exceeded and a non deliver report is sent to the sender or the mail server becomes available and the mail is sent on.

 

[speedracercjr]

I didn't do anything to fix it. We have had the same internet service for about 3 years with no problems. I just think that their DNS server was flaky or there were some network problems because we haven't had any problems since then, and up until then had never had problems before. The ISP we have does have anti-spam capabilities but we have it turned off as we do our spam filtering at the firewall level.