Subject: re: More information about installing/using imap.

From: Mark Crispin <[email-masked]>
Date: Thu, 26 May 1994 18:28:18 -0700 (PDT)

On Thu, 26 May 94 11:05:49 MST, C. R. Oldham wrote:
> I've recently become interested in imap especially since it
> supports accessing Usenet news.  However, I can't seem to find
> any information about installing and using the utilities.

This is really a question about the c-client implementation of IMAP as opposed
to an IMAP protocol question, and should probably be continued on the c-client
list instead of the IMAP list.

The technical notes that come along with Pine describe installation, as does
the README file.

> Do all users receiving mail via imap need an account on my machine?

This is normally the case in the c-client implmentation; however, you can
change this with some modification.  The file imap/c-client/log_???.c (there
are different files for different systems) has a routine called server_login()
which determines the authentication policy; as written it uses the information
from the /etc/passwd file.

Similarly, the file imap/c-client/env_unix.c has code which defines what the
interpretation of the ``system mailbox'' and the ``home directory'' is.

Although ``giving every IMAP user an account'' seems to be an unreasonable
burden, you have to consider what you want out of an IMAP user ID:
 1) unique user identifiers, and authentication of that user identifier.
 2) access control between user identifiers, so that a user cannot access
    another user's data without authorization.
 3) a place for the storage of the user's INBOX.
 4) a place for the storage of the user's secondary mailboxes.

When you add up all these needs, you quickly find that an alternative
mechanism requires at least as much work as an entry in /etc/passwd -- you
have to store the (userid/password/mailbox location) data somewhere, and you
have to have some mechanism for access control (which UNIX UIDs and file
protections generally accomplish).

We have dedicated servers which are imap-only and that users cannot log in to.
We enforce this by having their shells set so they can not log in, or set so
that only an exec of /etc/rimapd is permitted.

> Is there a FAQ for imap?

Not yet, but hopefully there will be once the dust settles on the
specification.