Peter Schultz wrote:
> Terry Lambert wrote:
> > If you look over the historical cases of this discussion,
> > you'll see that the answer always comes down to "make the
> > system more modular, so people can replace XXX with YYY and
> > quit bothering us; please send patches". 8-) 8-).
>
> Thanks for your help on this. I've been getting so many search results
> that I've been unable to determine the exact problem myself. So, one
> absolute requirement is that the system have both an mta, and an msa.
> When you say msa, does this include pop&imap capabilities?
MTA: Mail Transfer Agent; used for transferring mail via the
SMTP protocol to other platforms over the network; this
is where most security vulnerabilities surface, because
the port is generally open to public attack, if people
fail to use a proxy firewall.
MSA: Mail Submission Agent; used for local submission of mail
messages, for either later or immediate delivery by an
MTA or an MDA.
MDA: Mail Delivery Agent; used for delivery of mail that has
been submitted via an MSA to a mail transport or to an
endpoint; an MDA that delivers mail to local mailboxes
is called a "Local Delivery Agent".
MUA: Mail User Agent; used for interacting with an MSA and/or
a Message Store; usually an MUA can do both, e.g. the
program /usr/bin/mail operates "mbox" formatted message
stores located in /var/mail/$USER and ~/mbox by default.
MS: Message Store; an MS can be simple filesystem storage,
such as a single "mbox" format file (see "MUA", above),
or "maildir" format (one file per message), a POP3 or
IMAP4 database protected and accessed only via a wire
protocol, etc.. The MS is usually directly accessible in
some form through direct file manipulation by *some* form
of MUA.
Minimal requirements for supporting local mail to the root user as
a result of security script processing (for example) are an MUA,
an MSA, and an MDA.
Clear?
If you decide your MS is Cyrus IMAP from ports, for example, then
you will need to provide an MUA replacement for /bin/mail, minimally
for reading mail sent to root, since Cyrus keeps its messages in an
internalized database format not understood by /usr/bin/mail.
There are other examples where an impedence mismatch is possible, of
course, but you specifically mentiond POP3/IMAP4.
-- Terry
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