[Alpine-info] [TOOBIG] error saving messages

[Mark Crispin]

On Mon, 5 Oct 2009, John G. Bennett wrote:

> - Is the [TOOBIG] error coming from the remote server, or

>   Alpine? (I assume from the remote server.)


The TOOBIG error code is defined in RFC 4469, in an extension (CATENATE) 
to concatenate multiple message fragments to compose a single message. 
IMAP has a maximum message size limit of 4GB, and with multiple fragments 
(each of which can be up to 4GB) it is possible for a catention to be over 
4GB.

Alpine does not use CATENATE at all, much less in this example.  It merely 
uploads individual messages via the APPEND command.  APPEND is incapable 
of accepting a >4GB message, therefore the TOOBIG condition can never 
happen.

Some servers have a limit, smaller than IMAP's limit, of the maximum size 
of the message.  For example, Panda IMAP will not accept a message larger 
than 1GB.  UW IMAP has a similar limit.  However, the TOOBIG response is 
inappropriate for a server-imposed limit since it is specifically defined 
for a single message that exceeds the IMAP 4GB limit.

Some mail stores have a limit of the maximum size of the mailbox.  The mix 
format is not limited, but earlier formats (including traditional UNIX) 
often have a 2GB overall limit.  Once again, the TOOBIG response is 
inappropriate.

Your example shows that the Zimbra server advertises MULTIAPPEND, a means 
by which multiple messages can be uploaded in a single operation. 
Apparently, Zimbra has a limit as to how many messages can be uploaded 
with MULTIAPPEND, and your attempt with Alpine exceeded that limit.

This is a BAD bug in Zimbra.  MULTIAPPEND must not have any such limit, 
other than the physical capacity of the mailbox (which can't be the case 
because you can upload them one at a time).  The whole purpose of 
MULTIAPPEND is defeated by such a bug.

I invented MULTIAPPEND and wrote its specification.


> - Could/should Alpine cope better with such an error, since it

>   can save the messages individually?


By advertising MULTIAPPEND, Zimbra is specifically telling Alpine not to 
do single uploads.  The ONLY reason for a MULTIAPPEND to fail is if the 
messages can not be uploaded, no way no how.


> - What is the [TOOBIG] error supposed to mean?


As noted above, it means that a concatenation of message fragments 
exceeded 4GB.  But no message fragmentation concatenation is occurring 
here.


> - Is it appropriate for the remote server to issue this error

>   message under these conditions?


Absolutely not.

If Zimbra can not implement MULTIAPPEND correctly, it should remove that 
capability from its server.

-- Mark --

http://panda.com/mrc
Democracy is two wolves and a sheep deciding what to eat for lunch.
Liberty is a well-armed sheep contesting the vote.