Mail and reverse DNS question

[PWSowner]

Does reverse DNS on a server only need to be set up for the main server IP or for any IP used as a dedicated IP?

Why I'm asking is, I always thought it was just the main server IP, but I suddenly (sometime in the last few weeks) stopped being able to get emails from 1 customer. She's had no problems emailing for the last 4 years, but now her emails keep getting sent back to her after timing out. She contacted her ISP and they did some checking and couldn't find anything wrong. Their tech emailed me from the same domain as her email, and I had no problem getting his emails, but I can't get hers.

The strange thing is one part of the email that says:

<myemail@mydomain.com>:
xxx.xxx.xx.xx does not like recipient.
Remote host said: 451 Could not complete sender verify callout
Giving up on xxx.xxx.xx.xx.
I'm not going to try again; this message has been in the queue too long.

The xxx.xxx.xx.xx is my sites dedicated IP, not the servers main IP.

Does that mean my sites IP needs reverse DNS set up as well? Any ideas from that why she can't email me?

[PWSowner]

I'm still investigating and it looks like the problem is on her end.

I noticed in the exim config editor, "Use callouts to verify the existance of email senders.", and it's checked. Based on Chirpy's site, it sounds to me like my server is checking her address and the check fails so it's not accepting her emails.

Why are her emails failing, but emails from the tech guy from the same domain pass?

If I just uncheck that option her mail will likely go through, but does that mean more spam will too?

[rikgarner]

Hi Mike,
If you disable checking of the existance of domains for originating email addresses, you will likely find that you do get more spam, as domain-existance checks no longer take place, however, it depends if your using any other spam checking to go with.

I always get RDNS configured for all IP's used - companies like AOL will not permit relay in unless there is an RDNS entry.

www.dnsstuff.com has a fantastic array of tools for testing for that kind of thing, and I run a dnsreport.com on each domain after I migrate it in, just to check for the obvious.

Rich

[PWSowner]

I use Chirpy's mailscanner setup which is doing a nice job. I have it set to delete high scoring spam and I check the log of deleted messages now and then and have never seen a real email deleted.

I already did the dnsstuff.com tests and it found nothing wrong. I unchecked the verify options and did a test interac transfer and it worked, so that was the problem. I guess we can't use those options.

[foreigndude]

I'm having a similar problem where one of my clients doesn't get emails sent from certain people. I tested his email address with dnsstuff and it gave the same error (550). After I unchecked the same thing you did (Use callouts to verify the existance of email senders), DnsStuff now successfully connects to it and gets a good response.