Re: Internet host SMTP server survey 2003-11

Richard O. Hammer <[email protected]> wrote:
> Charles,Charles Cazabon wrote:
> > I looked up PTR records for 1000000 random non-RFC1918 IP addresses. 
> 
> Could someone explain for me the significance of PTR records to this 
> survey?

"Real" mail servers need a PTR record; many, many hosts will refuse all mail
from addresses without PTR records.  So if an address doesn't have a PTR
record, it is extremely unlikely to be a legitimate mail server.

> > Evidently the Internet now has about 278 million IP addresses with PTR
> > records.
> 
> How did you get this?  Is it a linear extrapolation?

Yes.

> >   57991 connections timed out;
> 
> Does this mean that the server accepted a connection on port 25, but 
> never said 220?

No, that's a dropped connection.  Timed out means I tried to connect, did not
establish a connection, and did not get a "connection reset by peer".

> What is the time out period?

A couple of minutes in my case; plenty long enough.

> When a connection times out, which machine cuts the connection, your client
> or the server?

?  It timed out without connecting.  There never was a connection to "cut".

Charles
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Charles Cazabon                         <[email protected]>
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