Here is a list of papers discussing the use of email in studying FLOSS (free, libre, and open source software) development.
(Disclosure, I run the flosshub site, and I wrote a few of those papers, including a survey of how FLOSS researchers have used email in the past, and what projects they've studied most)
I personally think that the MarkMail service is very handy for general studies of email. Here is a paper where we used Markmail to look at the use of pastebins over time on FLOSS projects. (Are they adopting pastebins as an innovation or not?) Markmail was a great source for that kind of "mile wide, inch deep" analysis where we were just counting words.
However for doing large text analysis, usually there is so much mail that most people don't use a service like MarkMail or Gmane, but rather they look for the original mbox files for the email. This is so that you can put them in a database and do your own cleaning.
Keep in mind that some projects like the LKML do not have the original mbox any more (a tragic loss, IMO) so you are stuck scraping your own data from various web sites that provide archives, such as lkml.org. Other projects, like Apache ones, DO have email archives where the mbox are available.
Keep in mind that if you are studying FLOSS, the messages themselves will be quite messy and very technical, full of source code, replies, and all kinds of garbage. Right now I am working on a data cleaning project with a 20-year set of email and it has taken nearly a full year for myself and a student to clean and process this mail properly.