[imp] Attachment sizes and linked attachments

[Tim Bannister]

> Jan Schneider schrieb:
> > the attachment size limits are applied no matter  
> > if the attachments are sent with the message or as linked attachments.  
> ...
> > Now, wouldn't it make sense to not use the same limits, or maybe even  
> > not use any limits at all, if you send files as linked attachments?  
> 
> It would certainly make sense to provide separate size limits
> for attachments and linked attachments. Normally, the size limit
> for linked attachments would be much larger than the limit for
> RFC-822 attachments.
> 
> 
> As we had already a "File Transfer" service (akin to Imp's linked
> attachments) in place, I had to modify imp/templates/compose/compose.inc
> to adapt it to our situation (no linked attachments, rather a link
> to our service). One reason not to allow linked attachments were
> storage, and backup, considerations: Imp's upload drectory can be
> kept small, and temporary (e. g. a RAM disk), when no linked attachments
> need to be kept for days, or even weeks.
> 
> For sites like ours, some configurable backend, or hook interfaces,
> for the linked attachments would come handy. It would be nice to exploit
> Imp's user interface for the linked attachments (including a note on
> the URL, in the message being composed), but still use some external
> service for the actual storage (and later retrieval) of the files being
> linked. I had not yet the time to think about the details of this
> proposition, hence I haven't filed a formal enhancement request. Any
> ideas?
> 
> Best wishes,
>    Otto Stolz

We use a similar configuration here (University of Manchester, UK). Our
users have storage for mail and for files, both stored centrally. At the
moment we run IMP on servers which are identical and don't need to
retain any data beyond the length of the session. Preferences are stored
in a lightweight database.

To avoid abuse (or misguided over-use), we would want to make "linked
attachments" count against the sending user's quota until they expire.
For the most part this wouldn't impact users as they usually retail this
kind of document long term. It does take the service partly out of the
scope of Horde / IMP; even if IMP offered something like this, we would
probably still need to customise it.

-- 
Tim Bannister
IT Services

e: Tim.Bannister at manchester.ac.uk
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