[CLUE-Tech] IMAP vs POP

[Carl Schelin]

--- "Jed S. Baer" <thag at frii.com> wrote:
> On Fri, 4 Jun 2004 16:00:12 -0600
> Jeff Cann <j.cann at isuma.org> wrote:
> 
> > POP downloads messages from the server onto the
> client machine.  So,
> > those messages are available only to the client
> that downloaded them.
> 
> But in Sylpheed, there's an option under the POP3
> settings for removing
> messages after retrieval. I have it checked, and I
> admit I've never tried
> unchecking it and seeing what happens.

Well, it sort of depends on the format the pop server
is using to maintain your mailbox. At my last job, we
supported 2000 or so users of which only 700 or so
were in the office on a normal day. The mail boxes
were stored in a mbox type format (qpopper).

When users saved e-mail on the server, the users mbox
file got larger and the download would get slower.
Multiply that by the 700 or so users and the others
who were at home, across the states or even overseas.
Dealing with the connection from France or Russia was
fun. Secure connections and routing through the State
Department over a 1200 baud link.

Anyway, consider a broadcast message to all users.
Typically these were really important messages such as
the death of an astronaut. The message would go out
and everyone who was logged in would immediately be
told of a new message and they'd automatically pop due
to a notify program (client side finger server).

Now consider the mechanism. Your client tells the
server to check your messages. The server runs through
your mailbox until it finds that a new message has
been appended. It then starts up again, going through
the mailbox copying it to the mailtemp directory until
it gets to the new message(s). These are given to your
client. Once they are done, the messages are then
moved back to the mail directory.

Since we were using Eudora and qpopper (both qualcomm
products), I discovered a problem. Messages were being
saved on the server but the client didn't have their
system configured to save mail. It turns out that if
you were saving mail, turned it off but didn't check
one more time before closing Eudora, the messages
would stay out there forever. In later versions, they
added a "clear server" option by clicking on the check
message button while holding down the alt key.

We had no mandate from the customer to restrict server
mailbox sizes. So the engineering folks would simply
build new, faster and larger servers. When I left,
they had built a new set of servers based on sun
blades (for the pop servers) behind a redundant pair
of F5's, a pair of cisco routers, and a SAN for the
data store. Many terabytes of storage.

But I'm not bitter.

> 
> jed

Carl


	
		
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