Exim has a set of documentation released with it. A text file of the main documentation is released as part of the exim tar archive. Additionally postscript and texinfo forms of the documentation are also available in separate tar archives on the ftp sites.
There is also a book, produced by the author - See the book website for further information.
New user documentation can be found at the Exim New Users site
User supported documentation, FAQs and hints can be found in the wiki.
There are 3 main sets of documentation for exim, all of which are also available below in html form.
The main user and configuration manual is the specification document