We have had an issue with email for a while. We have exchange 2010 behind an isa 2006 firewall. This is then on a virgin media big red connection. Also connected into this connection is our frog vle.
Some of our senders can send email to us with no problems. But we have some senders who can't and they get a ndr return of 554 5.7.1 relay not allowed. The thing is this ndr is not being returned by our exchange server, it is being returned by the ip address from our frog vle. All our mx records on the Internet are correct and external pings, nslookups and trace routes back correct.
We use the frog vle for our website which is using the same domain as our exchange email but not using the email on the frog vle with the same domain.
Has anyone any suggestions or ideas of what this may be? I have paid for engineering time for this issue and it has still not been solved.
Any help would be fantastic.
You could do with asking one of them what their DNS is and then running an MX query for your domain against it.
I use MX Lookup Tool - Check your DNS MX Records online - MxToolbox most of the time for testing.
I have got a few of them to check and they come back with the correct ip for the exchange server.
I have also used the various tools on mxtoolbox to check things and it comes back ok.
Where the domains ever in the control of the LEA (inc DNS) - could it be they still have legacy DNS records on their system?
Hi, I would ask the ISP to setup a reverse dns to your mail server. Use all of the tools on MX toolbox to instruct you. I use to have loads of problems sending and receiving to certain companies and LEA's due to this. It sounds like a very similar problem and error message that I had. Also maybe worth checking if the IP address has been black listed etc.
We had a similar problem when we switched ISP's. Our email used to come in via the LEA mail relay / filter. After we moved the LEA mail still came via the old broadband link, this was because they had configured their mail relay to send the messages to a specific IP rather than looking up the MX record. A quick change at the LEA and all was working again. So I would look to see if you can get full headers from these problem domains and see if there is anything common between them. It could be they are all using the same relay and that relay is configured to a specific IP rather than lookup to MX.
I think we have solved the problem now! We seemed to have had an issue with our external DNS. There were two conflicting DNS records set.
Thank you to everyone who helped!
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