[Dovecot] How to manipulate attachments with LDA?

[Piotr Szafarczyk - NetExpert]

On 2013-07-09 14:48, Robert Schetterer wrote
> depends on what you like to do exactly
>
> you may use sieve pipe ext prog
>
> http://wiki2.dovecot.org/Pigeonhole/Sieve/Plugins/Extprograms
> http://wiki2.dovecot.org/Pigeonhole/Sieve/Plugins/Pipe
>
> http://hg.rename-it.nl/dovecot-2.2-pigeonhole/raw-file/tip/doc/rfc/spec-bosch-sieve-extprograms.txt
>
>
> Best Regards
> MfG Robert Schetterer
>
I use pigeonhole 0.4, so I will play with extprograms. I was sure sieve 
cannot do such things.

Are you sure I can modify a message with the plugin? I see:
"The "execute" action does not change the message in any way"

All examples store messages in a folder instead of modifying them.

I need to replace an attachment or insert a new one into a message.