Email attachments

Josiah Carlson jcarlson at uci.edu
Sat Oct 23 05:53:18 CEST 2004


lutherrevisited at aol.com (LutherRevisited) wrote:
> Thanks, I looked into TOP and it looks like I'll be able to handle that issue
> satisfactorily with at least one, maybe many, but not all servers.

Perhaps you missed the later part of my post when I explained that the
location of attachments can be arbitrary.  That is, attached files can
come before what most people consider to be the body of the email (text
like what you are reading now).  At best, using TOP is a 95% solution. 
The 100% solution is to just download the email and call it good.

If you merely care whether there is an attachment or not, deciding based
on the size of an email (the sizes returned by LIST) can be reasonable.


> POP3 is not looking good to me now, but with Yahoo what can you do....

Well, with Yahoo, you can only access them via POP3 if you have paid for
their services.

Really, mail access comes down to the simple maildrop approach that is
all client-side (POP3), or the complicated server handles everything
approach (IMAP4).

With a simple approach comes a simple protocol.  POP3 servers and
clients can be implemented in an afternoon, and I have done so a few
times (it is what I get paid to do).

The IMAP4 spec is huge, and allows asynchronous command processing (the
server can reply to command B before command A when command A was given
first), which complicates matters.  Having written partial IMAP4 servers
and clients, I will tell you that it is not really approachable in
anything less than a weekend.

I believe that the reason why very few large webmail providers offer
IMAP4 access is due to the protocol being very difficult to get right,
and because POP3 does most of what is necessary.


In my opinion, what is really needed is a protocol that sits between
POP3 and IMAP4.  POP3 with folder support and a few other little pieces
would be sufficient to implement all the protocol necessary for a
full-on webmail service with the features of both Gmail and Yahoo Mail. 
Unfortunately, the liklihood of this happening and becoming widespread
is very low; both the POP3 and IMAP4 RFCs have been around for quite a
while, and many among the email community believe that they are
sufficient.

Ah well...
 - Josiah




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