Multiple Ip addresses for rDNS

We currently have a customer who has 2 adsl lines through a watchguard which is splitting and directing the traffic for outages.

They have their mail setup to only send from 1 line (say IP - line 1) which has a reverse dns setup for

If line 1 goes down, and we let the mail go out of line 2, the rdns will be incorrect, as its going out of  ip which has a reverse dns of - even though the servers banner is

Is there any way to have the rdns to 2 different IP's? or is there a better setup?

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I'd recommend asking the ISP if they'll relay SMTP for you, that way it doesn't matter!
Why not just have the ISP change the PTR record for the IP so that it points to  There shouldn't be a problem with multiple PTR records pointing to the same FQDN.
Jessie Gill, CISSPTechnical ArchitectCommented:

You could do the below or you will have get the ISP to relay for you or use a third party

Mx = 10 =

A = =
A = =

With the above email will be using round robin to look up but it will always go to your watch guard at which point the watch guard will send the mail to exchange.

Now the Rdns for both ip addresses should be So if you do end up switching they will still both have Rdns records.  Thus if line one fails, email will not be lost since now the email server trying to send will not be able to find the server it should do another lookup and get the other a record and then connect to your watch guard.   This is how I believe DNA will behave

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