info identifying my computer in emails sent from OE

Sometimes when people reply to my emails I see info identifying my computer in their reply. E.g.:

Received: from dell4100 (c-25-218-16-54.hsd1.ma.comcast.net[24.219.16.54])
by comcast.net (rwcrmhc12) with SMTP
id <20060724190042m1100rafn4e>; Mon, 24 Jul 2006 19:00:41 +0000
Message-ID: <016501c5af53$7309db50$3610da18@dell4100>

The above is a section of a reply I received a while ago to an email I sent (I randomized a few numbers in it). I run a Dell 4100. Why does the Dell 4100 info show in some replies I receive? Is it sent out with other email clients, or just OE? Is it sent if I use web-based email or just a local application? Is there a way to prevent sending info that uniquely identifies my computer? Why would some email clients include such information in the reply, but most don't? In a scan of the header info of a few emails I've received recently, I can't find any info about the make/model of the computer sending it... why?

 

I don't understand what you mean by "Only send when using a local application." Edit: oh, do you mean the computer name is sent only when I use a local application, not web-based mail?

I get plenty of mail that I'm pretty sure isn't sent from web-based mail, yet I can't find a computer name in the headers. Or not one as obvious as dell4100 anyway. So I'm thinking there's some way for me to continue to use an email app, but get rid of the header info.