Sometime Today, abhijeet assembled some asciibets to say:

 now,i understand that the sendmail daemon identifies me as
 abhije@localhost(when i telnet the port 25)-- i get
"IDENT:abhije@localhost.localdomain" as part of the response to
 HELO.
 when i say......

That's because you have an ident server running on your machine. I'd advise you to turn it off. I don't remember how, as it's been a long time since I did that. I think it may have to do with finger.

sendmail also determines your hostname from what is returned by hostname -f. If you want to specify it explicitly, then in your sendmail.cf, add/edit the line that says Dj and add your hostname to it. Alternately, add it in sendmail.mc and regenerate (preferred). I think it is confDOMAIN_NAME.

If your host has multiple names, add them to sendmail.cw. Only add full names here.

 MAIL FROM:someone@some.other.domain
 ....it responds that the sender's address should resolve.....what
 does that mean???

This is to block spammers. It's understood that if a server does not exist, then there can be no emails from there. If an address does not resolve, it means that it doesn't have a DNS entry.

Since you're probably on a dial-up line, you won't have continuous DNS, but, since you only receive email when you are connected to the net (and DNS is up), this isn't really a problem; unless you're trying to simulate it like above.

 i thought because it sends mail ......it should accept all sender
 addresses!!!

Nope. It should only allow senders who are allowed to use it, otherwise spammers could use your server to send mail from anyone to anyone.

The way sendmail is configured (I hope), is to accept mail from anyone provided it goes to a local mail box, or comes from a local user.

 At the same time.....if i say
 MAIL FROM:some_other_login_on_my_linuxbox@localhost
 the mail is sent....even if "some_other_login_on_my_linuxbox" knows
 nothing about it!!!

That is true. Think about it this way. If you use netscape to send mail. Let's assume for the moment that you have two vsnl accounts. You use only one of them for mail, but connect to the net using the other one. Even though you are logged in as one user, you can send mail as the other. In fact, who you send mail as has nothing to do with who you are logged in as, or whether you're logged in at all. The mail server runs on its own, ignorant of any other servers running, or any other open session.

 my argument is that if it knows that i am abhije@localhost...and
 hence does not accept someone@some.other.domain....how does it
 accept mail from some_other_login???

Actually, if you telnet to port 25, it has no way of knowing for sure who you are. It does an ident on your client, but that can be disabled. If you run sendmail on the command line (using sendmail -bs), then it will add a warning header - X-Authentication-Warning: xxxx owned process doing -bs or something like that, basically saying who actually started the sendmail process. If you send mail from a CGI script, you may notice this. You'll also notice this on mails that I send from the office.

 i am new to sendmail..and smtp..could somebody help????
 i know i could use something less scarier than sendmail.....but i
 need to know what's happening here......

Sendmail's not scary. As long as you deal only with the mc file and not the cf file. The actual mail interface is common to all MTAs.

2.> Also is there some other mail client that has the address book facility???....i just need a break from pine.....

mutt, and if you want GUI, then balsa, nemh, netscape, etc.

3.>I also have a yahoo inbox.....but the yahoo server doesn't flush the mail when polled!!!! could somebody explain that???? (yes..i have registered for pop3 access)

Do you have option keep in your fetchmailrc? That's probably why. My yahoo mail is flushed alright.

Philip