Re: [exim] Exim / POP3 with Compressed mails

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Author: Nigel Metheringham
Date:  
To: exim-users
Subject: Re: [exim] Exim / POP3 with Compressed mails
On Tue, 2004-08-31 at 15:09 +0200, Charlie Elgholm wrote:
> Hi!
>
> Is there anyway to make Exim compress the mail when saving in in the users
> maildir?
> For instance:
> post_save_command = bzip2 $file_name


Ugh - maildir implementations have enough fun with filenames changing to
implement flags without you tagging a .bz2 on the end,.

> On the other hand, is there anyway for the Courier POP3D daemon to
> "uncompress" the file before streaming them to the user via TCP/IP??


I'd be surprised if there was an implementation of this for courier.  As
well as the already stated reasons of disk being cheaper than CPU, there
are other reasons:-
      * Courier is primarily an IMAP server not a pop server
      * As an IMAP server it needs to get access to the various
        components of the MIME message, rather than treat the message as
        a whole.
      * This means it probably needs to seek to specific parts of a
        message.
      * Seeking within a simply compressed file can be a real bitch -
        you typically have to rewind to the start and byte count from
        there.  To get round this you need to save it as a set of
        compressed MIME components
      * and BINGO you have just invented a mail storage database....


Theres a chance you could do something funky with appropriate use of
zlibc - and depending on your usage patterns and hardware you might find
the CPU is not so much of a problem as some people have indicated (crap
IDE hardware can use significant CPU transfering to/from disk, however I
am unconvinced that the savings would be worth it).

    Nigel.


-- 
[ Nigel Metheringham           Nigel.Metheringham@??? ]
[ - Comments in this message are my own and not ITO opinion/policy - ]