[TriLUG] OT: ATT UVerse internet access

[Matt Pusateri]

On Mar 31, 2011, at 2:23 PM, Chris Merrill wrote:

> On 3/30/2011 3:29 PM, bak wrote:
>> I got around this by using the 'submission' port. Modern UNIX MTAs have
>> this turned on by default. It is basically just
>> SMTP-with-authentication-by-default; no relaying. The well-known port is
>> 587. See RFC2476.
> 
> I was not aware of this port.  But I'm a little confused about the "no relaying"
> part.  If I am using it to send email to our customers, is that not relaying?
> If not, then I don't understand the distinction. I thought contacting an SMTP
> server to send e-mail to a user on some other server IS relaying ???


Chris,  when you as chris at webperformance (through your MUA - Mail User Agent, mail client, outlook, thunderbird etc)  contacts your mail server(MTA - Mail Transfer agent, sendmail, postfix, etc) (let's say mail.webperformance.com), you generally do so as an authenticated user, and thus are permitted to send mail through that mail server.   Now most properly configured mail servers today are setup to only allow mail from hosts and or users on their domain, either through host/network or user access rules. This is done to prevent others say me(matt at myficticiousdomain.org) from using your server to send my email.  When I send email as matt at myficticiousdomain.org through mail.webperformance.com, I am then relaying mail through your mail server.  This relaying of mail can happen for two primary reasons.  1. Your mail server could be an open relay allowing anyone to send unauthenticated mail through it.  2. I could have an account on your mail server say matt at webperformance and I could authenticate to mail.webperformance.com and send mail from my personal domain of matt at myficticiousdomain.org.


So whether you are connecting to your mail server in the office or at home, is really irrelevant, what is important is that your mail server is accepting mail from you as an authenticated user of mail.webperformance.com.   


Does that make it more clear?


Matt P.