changing Sendmail server's IP address, nightmare!

Derek Ragona derek at
Sun Feb 26 07:10:13 PST 2006

As far as I know, sendmail uses DNS and the server's name resolution it is 
running on for the IP's.  There is nowhere I know in sendmail where an IP 
is hard coded.  If you are having any difficulty it is due to changes to 
your DNS, and the time it takes for DNS changes to propagate across the net.

It sounds like you were doing too many changes at one time, moving to a new 
ISP which would require a change to all your IP addresses, AND changing 
your DNS from internal to the ISP's.

In making these changes you need to first get on your new IP block, so you 
have internet access.  Then update your DNS records for the new IP 
addresses.  Then as a last step move the DNS to your ISP, making your 
server's DNS a slave DNS or just a caching DNS server.

In making a move to your ISP's DNS be aware ISP's do NOT usually update 
their DNS maps often, typically once a week, then the new maps begin 
proliferating which usually takes 24-72 hours.

Hope this helps.


At 09:35 PM 2/25/2006, Curtis Hart wrote:
>   Does anyone have any specific information on making IP address changes 
> to Sendmail servers since I have found that this situation is a lot more 
> difficult/tedious than I had thought.  The Sendmail server in question is 
> also providing DNS for a web server, but I would like to use our new 
> ISP's DNS info for our web domains and for the mail server.  In a 
> nutshell, I recently started working for a small business that has a mail 
> server and web server, this occurred just after they had already begun 
> switching to a new ISP (Mpower).  I thought I knew enough UNIX/sys admin 
> info to make this happen but this has turned into a minor nightmare for 
> me, since Sendmail has so many files that may contain the old IP info.
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