550 Sender verify failed because of Incorrect Hostname

[Bradl3y]

I found out we were getting rejected by some servers because our hostname was setup incorrectly.

We had updated the host name to be a valid FQDN a long time ago in the Basic WHM setup, but we neglected to update it in the Network Setup.

I am going to call the new hostname: new.mynewdomain.com
The old hostname: old.myolddomain.com

[good] new.mynewdomain.com now resolves an IP successfully.
[good] when i type "hostname" on the server i get "new.mynewdomain.com".
[good] When i send an email to my personal gmail account, and check the headers, old.myolddomain.com is nowhere to be found, just new.mynewdomain.com.

[bad] When I send an email to an account on one of our other servers, it gets rejected that it can not verify the sender. When i look at the /var/log/exim_mainlog, it shows:

 no IP address found for host old.myolddomain.com

Why would the other server still be checking old.myolddomain.com?

[mtindor]

That might be a reverse DNS issue.

'nslookup old.oldmydomain.com'

Then, do an nslookup on the ip address it returns such as 'nslookup xxx.xxx.xxx.xxx'

See if 'nslookup xxx.xxx.xxx.xxx' returns the old name of the server or the new name of the server. If it returns the old name, get the folks who provide rDNS (reverse DNS) for your IP space to change the reverse DNS PTR record for that Ip address so that it references the new hostname.

Mike

[Bradl3y]

That might be a reverse DNS issue.

'nslookup old.oldmydomain.com'

Then, do an nslookup on the ip address it returns such as 'nslookup xxx.xxx.xxx.xxx'

See if 'nslookup xxx.xxx.xxx.xxx' returns the old name of the server or the new name of the server. If it returns the old name, get the folks who provide rDNS (reverse DNS) for your IP space to change the reverse DNS PTR record for that Ip address so that it references the new hostname.

Mike

Thank you, this was helpful. For the record though I had to do a nslookup on new.mynewdomain.com, then do a nsloopkup on the IP returned to see that the old.myolddomain.com was still being used as the reverse dns. Doing a nslookup on old.myolddomain.com just gave me information for a domain I no longer own.

Now, this is a dedicated server which I have root access to, I have a dedicated IP, is the rDNS still something that our datacenter has to correct or can I add this entry myself? I have submitted a support ticket to them but if I could take care of this myself I would obviously rather do that. Thanks for your help

[mtindor]

Thank you, this was helpful. For the record though I had to do a nslookup on new.mynewdomain.com, then do a nsloopkup on the IP returned to see that the old.myolddomain.com was still being used as the reverse dns. Doing a nslookup on old.myolddomain.com just gave me information for a domain I no longer own.

Now, this is a dedicated server which I have root access to, I have a dedicated IP, is the rDNS still something that our datacenter has to correct or can I add this entry myself? I have submitted a support ticket to them but if I could take care of this myself I would obviously rather do that. Thanks for your help

When you are on a server in a datacenter, many datacenters give you the ability to maintain your own rDNS (but usually you arrange that with them first, and usually this is only if you have a number of IP addresses). For the most part, your upstream or colocation/dedicated server provider usually maintains reverse DNS.

It is probably best to have them do it this time - and then if you really want to do it yourself, ask them if that option is available. Some places may have an interface of their own which customers like yourself can log into in order to modify rDNS entries for the IP addresses you have for your server. But you did the right thing - the ticket to your datacenter was the right step to take at this point. After they fix the current problem you can dialog with them if you want to see if they have a method for you to maintain rDNS for your IPs yourself.

Of course, if you only have a few IPs, most of them are not going to change very often and it is just as easy to open a ticket with your server provider and have them update it on the rare occasion that you need it done.

- Mike

[Bradl3y]

Thank you, they updated the rDNS for me, and I am still getting emails rejected from our one server to the other server, with the sender verify failed. It does not give any errors about the host not being found anymore in the exim_mainlog, so the receiving server recognizes and accepts the rDNS now, however, i still get this:

2007-07-25 14:16:51 H=new.mynewdomain.com [xxx.xxx.xxx.xxx] sender verify fail for <me@mynewdomain.com>: The email address does not exist.
2007-07-25 14:16:51 H=new.mynewdomain.com [xxx.xxx.xxx.xxx] F=<me@mynewdomain.com> rejected RCPT <brad@my2ndserver.com>: Sender verify failed

They are both WHM/cPanel 11 servers.