In kmail 2.1 I can't search my mail anymore. I mean
I can open a search window but I get zero results (even
if I can see the mail I'm searching for right there in
the current folder).

I assume I need the nepomuk / strigi stuff to get
kmail search working ?? Is that right?

Unfortunately, if I turn on nepomuk / strigi my
computer explodes (so to speak)

I don't think that having nepomuk enabled fixes this. I have nepomuk enabled and akonadi has fed all my emails into it. I get no results in the search function, too. I can only assume that the search function is currently broken.

However, having nepomuk enabled provides a solution of sorts — I can search for emails using krunner and get results there. I suppose you can also tag emails and search using those tags... but I still miss having a working Search function within kmail...

The search function works for me, even though it is really slow and I'm not sure how reliable it is. What's neat though is that it saves the searches as some kind of folder.

For me, it doesn't even seem to do anything. It briefly blinks when I hit Search and there's always 0 results.

But the saved searches thing looks pretty nice. When kmail in particular and akonadi in general gets over the initial bug fixing, its features look very promising. Can't wait to use them...

I've found something interesting.

I turned on nepomuk -- NOT strigi, just the "semantic
desktop" part and now search works in kmail

unfortunately, the search results are

1. incomplete (seems to randomly miss some things)
2. the search results include a bunch of blank results
3. you can't tell what folder the hits are in
4. you can't restrict the search to particular folders

I guess this is progress however

Yeah, Nepomuk is the server storing all kinds of information about you. There's many inputs and outputs. Strigi, which is a service that scans your files is one of the inputs. Akonadi has its own feeder processes that feed data into nepomuk.

I have it turned on (and make use of it often). The emails have clearly been indexed (I can get results through krunner's nepomuk agent), but my search results in kmail are still blank.