We need a new subject- bug fixes

[David G. Miller]

Timothy Murphy <tim at birdsnest.maths.tcd.ie> wrote:

> Tim wrote:
>
>   
>> > I've never had Linux accepting mail from the internet with its SMTP
>> > server, in all the years that I've used Linux.  And only those with
>> > their own domain name and/or fixed IP address could to that, either.
>>     
>
> I just started trying this last week, more as "proof of concept"
> than a serious matter.
> I found changing sendmail.mc fairly simple.
> In addition to commenting out the line that was mentioned,
> I also commented in the LOCAL_DOMAIN line (with appropriate domain);
> I'm not sure if that is actually necessary?
>
> I've been warned that what I did was very dangerous,
> so I'll probably close it down,
> unless I find a simple way to stop it being an "open relay".
>
> Incidentally, I also had to open a peephole in my ADSL modem,
> and add a rule to shorewall to allow email in.
The next trick is to set up a nameserver that points to your domain and 
serves up MX records that point to your system.  You need a domain name 
(check around for registrars to see who has the best price) and a 
nameserver (check out somebody like DynDNS).  If you already have a 
static IP address, your registrar will probably do nameserving for you.  
If you don't have a static IP address, you'll need somebody like DynDNS 
to do nameserving of the dynamic IP address your ISP assigns.

Once you have that stuff sorted out you can try sending e-mail to 
yourself using gmail, Yahoo Mail, etc.  If you get this far, you can 
then also verify that you haven't configured your system as an open 
relay and any other tests you want to try.  If you want to have your own 
mail server, this is also a good time to configure and test any server 
based spam filters you want.  At this point you technically have a mail 
server but, since no one knows about it, you are pretty safe having it 
up and running while you test. Until you are sure you have it configured 
properly, close the port at the router unless you are testing. 

Once you are sure you have everything configured properly you can 
consider keeping your server up and open and giving out you "personal" 
e-mail address.  The gotcha is that, for e-mail to be useful, you need 
to have the mail server up and on-line all of the time (or pretty close 
to it).  If you really want to use the e-mail address, you need to think 
about how to back up your mail server, maybe a UPS, RAID, etc.  These 
are all things your ISP hopefully already does for you.

One final "fly in the ointment" is your ISP may not allow you to run any 
servers unless you pay for a commercial account.  Check your terms of 
service.

Cheers,
Dave

-- 
Politics, n. Strife of interests masquerading as a contest of principles.
-- Ambrose Bierce