strigicmd create -t clucene -d index/ mail.tarIt took Strigi about 30 seconds to index the whole archive. That's good performance!
Now, Strigi indexes content full text, but also uses a controlled vocabulary (among which one specifically for chemistry). So I can search for email messages which have article in the subject with:
strigicmd query -t clucene -d index/ email.subject:article
However, From: and To: content was not yet extracted. That was easily patched. This allows me to find correspondence between me and, for example, Christoph:
strigicmd query -t clucene -d index/ email.to:Christoph AND email.from:Egon