Iljitsch van Beijnum wrote:
On 27 feb 2004, at 0:26, Bruce Lilly wrote:
If the mailbox is accessed via a standard network protocol such as
POP or IMAP, it is trivially easy to switch MUAs.
Not quite. Then the new MUA must download all the messages again from
the server.
Not with IMAP, where the message store typically lives on the
server (which could very well be the same machine -- the point
being to delegate management of the storage to a specific
piece of software other than the UA per se).
A flat file just doesn't
work well with even a modest number of messages.
It can work if you build an index and don't go around removing message
from the middle of the file too often.
Cyrus IMAP stores one
message per file, with a database for metadata (access lists,
etc.), and it's quite fast.
Maybe for random access, but if you need to access all messages you're
bound to be slower. Also, the file system overhead makes this a pretty
bad idea.
Not necessarily. Consider a POP UIDL command, which lists the
messages by UID with each message size. With a flat file, every
byte of every message is read as the sizes are determined and the
IDs generated. I used such a system -- it became unusable with a
few hundred messages; it took several minutes to generate a UIDL
response. Cyrus IMAP (using POP protocol) on the same hardware
with approximately 40000 messages completes the UIDL response in
a fraction of a second (generating it is simple -- each message
file is named according to the UID, and a simple stat() system
call gives the message size; there's no need to read each file).
What I imagine is a system where messages are stored in a binary
container format
[...]
I don't want to get too far into the details at this time, but
a binary format is only acceptable if a text message is still
recognizable as such. The ability to use tools such as find
and grep is very important, not only to users, but administrators
as well -- when the pointy-haired boss says "I know I have a
message from John Smith somewhere, but I can't find it", would
you rather rummage around in a single 300 MB file (possibly in
a binary format), or just run something like
grep -i "john smith" /var/spool/imap/users/phb/inbox/*
? For that matter, IMAP provides search capability with
server-side support, so it's possible to search messages
regardless of the client MUA, without having to keep
copies of the messages for each MUA.
Standards improve quality, because they usually eliminate inferior ways
of achieving a result. And often vendors that implement their own
solution also support the standard to some extent in order to be
compatible.
Among standards-conforming implementations, there can be a substantial
difference in the quality of implementation. And some vendors
that pay lip service to standards are often the cause of
interoperability problems through non-standard "extensions"
and/or broken implementations (e.g. HTML/CSS).