Authentication: how does it work?

9 msg	Maximum length of a header line?
3 msg	Delay splitted in logfile
4 msg	Customize the 221 Bye message
1 msg	Postfix snapshot 20070724
8 msg	relay access denied
5 msg	spamcop link to my website in signature leads t...
13 msg	Message size limit per user
4 msg	chaining aliases failing?
5 msg	misdelivery of mail to user@virtual to user@domain
2 msg	Vacation Message - request for comment on imple...
10 msg	Possible DoS when the adress and the virtual my...
1 msg	Postfix + Dovecot + Procmail
7 msg	2 instances of smtpd in master.cf
2 msg	diskless client with link to servers mailqueue

Authentication: how does it work?
\ David Brachet (24 Jul 2007)
. \ Patrick Ben Koetter (24 Jul 2007)
. \ Benjamin Schmidt (24 Jul 2007)
. . \ David Brachet (24 Jul 2007)

1 msg	uupth or pathto in Postfix
3 msg	SASL and NIS errors
1 msg	postfix sqlite ??
2 msg	Problem authenticating postfix users with cyrus...
19 msg	sender address verification vs. script-generate...

Subject:	Authentication: how does it work?
Group:	Postfix-users
From:	David Brachet
Date:	24 Jul 2007

Hi all!

I would like my postfix asks my users to authenticate, only when they are
not in the local network. Is it possible? Perhaps Postfix make that
automatically?

Another question: if authentication is activated, how does it work if I
would sent a mail from a webmail like IMP?

Thanks