CentOS 4.6
Hi All:
Is it possible to force sendmail to use a specified host name for outbound email to a selected domain name instead of the host name that can be found by looking up the DNS entry?
The problem is that we have a client that uses the same ISP as we do and the IP addresses assigned to both of us are very close. This has resulted in connection problems specifically with our outbound email to the client. I believe it is an issue with TCP/IP routing. In the past the ISP has setup some sort of special routing that redirects our email to the ISP's backup mail server which then delivers the mail to the client. Every once in a while the ISP does something with their configuration and the routing override is lost for several days until we can get them to recognize the problem and then figure out what they did the last time. This happened over the weekend and we are still waiting on the ISP to fix it up.
My thought was can we configure this in our mail server so that we and our client do not have to suffer with this again?
TIA
Regards, Hugh
On Wed, 09 Apr 2008 19:54:28 -0700 Hugh E Cruickshank hugh@forsoft.com wrote:
Is it possible to force sendmail to use a specified host name for outbound email to a selected domain name instead of the host name that can be found by looking up the DNS entry?
I'm not entirely sure that I understand your problem. If you have a unique domain name, and your client also has a unique domain name, and your dns records are properly configured, then sending email from domain name A to domain name B should just work, regardless of how close your actual IP addresses are.
Having said that, you can put a domain name and IP address in /etc/hosts on the originating computer and that computer will henceforth use the IP address specified there.
From: Frank Cox Sent: April 9, 2008 20:01
On Wed, 09 Apr 2008 19:54:28 -0700 Hugh E Cruickshank hugh@forsoft.com wrote:
Is it possible to force sendmail to use a specified host name for outbound email to a selected domain name instead of the host name that can be found by looking up the DNS entry?
I'm not entirely sure that I understand your problem. If you have a unique domain name, and your client also has a unique domain name, and your dns records are properly configured, then sending email from domain name A to domain name B should just work, regardless of how close your actual IP addresses are.
I agree whole heartedly that it "should just work" but time and time again we have see where it does not work.
Having said that, you can put a domain name and IP address in /etc/hosts on the originating computer and that computer will henceforth use the IP address specified there.
That would work if I was looking to use a specific IP address but would like to use a specific host name. For example I would like all mail outbound to example.com to bypass the DNS/MX entry of mail.example.com and use instead backupmx.isp.com not just the IP Address of backupmx.isp.com.
Thanks muchly for your suggestion.
Regards, Hugh
Hugh E Cruickshank wrote:
From: Frank Cox Sent: April 9, 2008 20:01
On Wed, 09 Apr 2008 19:54:28 -0700 Hugh E Cruickshank hugh@forsoft.com wrote:
Is it possible to force sendmail to use a specified host name for outbound email to a selected domain name instead of the host name that can be found by looking up the DNS entry?
I'm not entirely sure that I understand your problem. If you have a unique domain name, and your client also has a unique domain name, and your dns records are properly configured, then sending email from domain name A to domain name B should just work, regardless of how close your actual IP addresses are.
I agree whole heartedly that it "should just work" but time and time again we have see where it does not work.
Having said that, you can put a domain name and IP address in /etc/hosts on the originating computer and that computer will henceforth use the IP address specified there.
That would work if I was looking to use a specific IP address but would like to use a specific host name. For example I would like all mail outbound to example.com to bypass the DNS/MX entry of mail.example.com and use instead backupmx.isp.com not just the IP Address of backupmx.isp.com.
Thanks muchly for your suggestion.
Regards, Hugh
Hi, It has been some time since I have had to do anything with Sendmail like this, but I believe mailertable is what you need. See http://www.sendmail.org/m4/mailertables.html
Hope this helps :)
From: Clint Dilks Sent: April 9, 2008 20:32
Hi, It has been some time since I have had to do anything with Sendmail like this, but I believe mailertable is what you need. See http://www.sendmail.org/m4/mailertables.html
Give the man a cigar! That looks like precisely what I need.
Hope this helps :)
I am sure it will.
Thanks muchly!
Regards, Hugh
From: Hugh E Cruickshank Sent: April 9, 2008 20:43
From: Clint Dilks Sent: April 9, 2008 20:32
Hi, It has been some time since I have had to do anything with Sendmail like this, but I believe mailertable is what you need. See http://www.sendmail.org/m4/mailertables.html
Give the man a cigar! That looks like precisely what I need.
Well that did seem to work. At least the email is being delivered to the ISP's backup mail server now. I will not know until tomorrow if the mail actually makes it through to the client but then that an issue between the client and the ISP.
Thanks again.
Regards, Hugh
Hugh E Cruickshank wrote:
From: Clint Dilks Sent: April 9, 2008 20:32
Hi, It has been some time since I have had to do anything with Sendmail like this, but I believe mailertable is what you need. See http://www.sendmail.org/m4/mailertables.html
Give the man a cigar! That looks like precisely what I need.
Note that you don't need to do the makemap stuff - that's already include in the Centos setup. Just put the text suggested in the mailertable file and restart sendmail. And if you use a literal IP address, enclose it in []'s like it says for hostnames where you want to avoid the MX record lookup.
From: Les Mikesell Sent: April 9, 2008 21:10
Hugh E Cruickshank wrote:
From: Clint Dilks Sent: April 9, 2008 20:32
Hi, It has been some time since I have had to do anything with Sendmail like this, but I believe mailertable is what you need. See http://www.sendmail.org/m4/mailertables.html
Give the man a cigar! That looks like precisely what I need.
Note that you don't need to do the makemap stuff - that's already include in the Centos setup. Just put the text suggested in the mailertable file and restart sendmail. And if you use a literal IP address, enclose it in []'s like it says for hostnames where you want to avoid the MX record lookup.
All that was needed was to add the entry to /etc/mail/mailertable and run "service sendmail restart". It rebuilds the database for you. I did not worry about the IP Address or the MX but it seems to have worked anyway.
Regards, Hugh
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Clint Dilks -
Frank Cox -
Hugh E Cruickshank -
Les Mikesell