[ubuntu-uk] Setting up mailserver

Martin Meredith mez at ubuntu.com
Sun Dec 28 10:31:41 GMT 2008

On Sun, Dec 28, 2008 at 08:58:46AM -0000, Ian Pascoe wrote:
> Morning All
> This is somewhat uncharted terrotory for me, in fact I know that little on the 
> subject I don't even know the correct questions to ask!  However, let's hope 
> this makes sense!
> If I wanted to set up a file / mail server at home, and be able to connect to 
> it through the internet, if the ADSL connection is dynamic, how does the DNS 
> server (I presume that's the only way of maintaining the link) know the 
> correct IP address to link to after the ADSL connection has been dropped and 
> comes up again with a new IP address?
> I presume that if the servre was physically moved to a different location, it 
> wouldn't matter as long as whatever method satisfys the previous question, it 
> would just re-connect itself and be off?
> This is something I've been thinking about doing for some time, and if anyone 
> can point me to some resources that would get me started so that I can build a 
> basic understanding up, and then start to be able to ask the right questions, 
> I'd be grateful.

Dyndns etc provide services that allow you to setup a domain name that will 
change it's DNS when contacted by you.

Put simply, a dynamic DNS service needs to be told every time your IP address 
changes. When this happens, it updates the record for your domain name to point 
to the new address. Generally, these use a low TTL (time to live) so that DNS 
servers at, for example, your ISP, will query their DNS servers (with the 
up-to-date record for your IP address) on a regular basis, rather than caching 
it (which is why you generally find when you make DNS changes on a "control 
panel" style site, it says that you may have to wait up to 48 hours - this is 
for the TTL to expire, so the DNS server checks against the server holding the 
record, rather than their internal cache)


Is a good place to start reading.

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