A Records and MX Records - are they linked?

[MarkDym]

Hi

I have a question concerning the relationship between MX Records and A Records. Please bear with me on this, as I am still learning about DNS.

We have just started using Mercury32 SMTP server to deliver our mail. This is sent from our private IP address and emails are sent with one of two domain names: apsarchaeology.co.uk or lincsheritage.org. Although we own these domain names, neither are associated with our private IP address. The domains are each hosted by different ISP's, and our Internet connection (and private IP address) is provided by a third ISP. Our SMTP server identifies itself as apsarchaeology.co.uk.

What is happening is that some mails that use the lincsheritage.org address are being returned with a 550: Verification Failed message. I have searched for information about this, and as far as I can tell it is to do with the fact that the reverse DNS is failing. I assume this is because our private IP address is not resolving to apsarchaeology.co.uk.

We have the ability to manage the apsarchaeology.co.uk domain's DNS through a web interface. The DNS options allow us to change the A records for various subdomains such as ftp, mail etc. What I would like to know is if we change the A Record for mail.apsarchaeology.co.uk from the ISP's assigned IP address to our private one, will this allow the reverse DNS to complete successfully and prevent further 550 Verification Failed error messages?

Also, we have just started using MessageLabs email service to eliminate the 10,000+ spam messages we are receiving each week. This involved changing the MX records so that they pointed to the MessageLabs servers rather than mail.apsarchaeology.co.uk. If the A record is changed, will this affect the MX records?

When mail arrives at the apsarchaeology.co.uk domain does it look for the A record, go there, and then look for the MX record? Or, can the A records and the MX records be accessed independently of each other?

I am still trying to understand how this works, so any help with this will be appreciated. I don't want to break our email if I can help it.

Thanks

Mark

 

[paella33]

You internet provider should setup the reverse DNS on your IP address, not your domain provider.

 

[MarkDym]

Thanks for your reply.

I've spoken to the people that provide our IP address, and they say that we need to speak to the people who manage our email domain (aps...)and ask them to setup reverse DNS from our private IP address.

Mark

 

[paella33]

That is incorrect IMO.

 

[MarkDym]

Thanks again for your input on this.

I assume therefore, that setting up reverse DNS is something that only an ISP can do. My problem is that I do not understand the difference between reverse DNS and changing the A Record to point to our private IP address.

I am presently trying to discover resources about how this works - there is plenty of information about separate aspects of DNS but I would like to read something that describes completely how emails are sent and received. Can anyone recommend a good technical resource please?

In the meantime, I'll keep searching.

Thanks

Mark

 

[paella33]

It's the reverse. If I want to know the IP address of your domain I use "regular" DNS. If I want to know the NAME of some IP address, I need to have setup reverse DNS. Try Wikipedia for this (and everything else )

 

[MarkDym]

aha! Many thanks! All it takes is a little nudge in the right direction. I'll check out wikipedia too.

Cheers!

Mark