[nzlug] Biting the Bullet -- Authentication & Email

[Cliff Pratt]

Daniel Pittman wrote:
> Cliff Pratt <enkidu at cliffp.com> writes:
>> Leon Matthews wrote:
>>> Also, is it a terrible idea to setup and use an IMAP server as a
>>> place just to physically store emails?  That is, let 'Evolution' and
>>> 'Mac OS Mail' handle delivery via our ISPs SMTP servers and our
>>> existing POP accounts. Running a mail domain seems  like it would
>>> take  more time than I have spare, and our ISP seems to be doing an
>>> adequate job of it for us.
>> IMAP servers don't store email. They look at individual mail
>> directories and allow the users to view their mail through a GUI (or
>> possibly a TUI).
> 
> *Some* IMAP servers store mail in individual directories.  Others store
> it in a database, others in traditional mbox files[1]; IMAP implies
> absolutely nothing about the back-end storage format.
> 
> IMAP, by design, is a protocol and storage engine designed to store
> email and similar data.  It specifies the interface to storage not the
> structure of storage.
> 
>> A mail server receives email from everywhere and delivers it to mail
>> boxes/directories. Then an IMAP server allows you to look at it.
> 
> Some implementations work that way.  Cyrus IMAP requires that delivery
> be handled via the LMTP protocol only; it uses an internal database
> built around the file-system but doesn't permit direct access to that
> data.
> 
> 
> None of which really is much of a muchness for the original poster who
> wondered about the value of setting one up -- I just wanted to correct a
> few misstatements in your comments.
> 
I don't think that they are misstatements, Daniel. IMAP servers are 
simply and only a means of delivery of mail which resides somewhere on 
the system. They are not storage systems. They use them.

The simplest 'storage mechanism' is, as I said, individual mailboxes, 
usually under a user home directory. The next simplest is a single 
'mailbox structure' separate from the user's home directory. The third 
simplest is to store the mail in a database.

In all cases it is the imap server's responsibility *only* to locate and 
deliver the mail to the mail client. It is *not* concerned with storage 
of the mail - that is the responsibility of the file system or the 
database system.

Similarly, the mail is delivered into whatever storage system is desired 
by the MTA - sendmail, exim, qmail, whatever. This storage system is 
*shared* by the MTA and the IMAP server. It does not belong to either.

For example, on my systems I use exim to receive mail into my mailboxes 
and vmailboxes, and I use Courier-IMAP to access them. I don't consider 
that Courier-IMAP stores any mail itself.

Cheers,

Cliff