The courier project's CVS data is in read-only mode, so the project may have switched over to another source-code-management system. To check, visit the Project Summary Page for courier and see if the menubar lists a newer code repository, such as SVN or Git.
The CVS data can be accessed as follows.
You can run a per-module CVS checkout via pserver protocol:
cvs -z3 -d:pserver:anonymous@a.cvs.sourceforge.net:/cvsroot/courier co -P common
cvs -z3 -d:pserver:anonymous@a.cvs.sourceforge.net:/cvsroot/courier co -P cone
cvs -z3 -d:pserver:anonymous@a.cvs.sourceforge.net:/cvsroot/courier co -P courier
cvs -z3 -d:pserver:anonymous@a.cvs.sourceforge.net:/cvsroot/courier co -P images
cvs -z3 -d:pserver:anonymous@a.cvs.sourceforge.net:/cvsroot/courier co -P liblog
cvs -z3 -d:pserver:anonymous@a.cvs.sourceforge.net:/cvsroot/courier co -P libs
cvs -z3 -d:pserver:anonymous@a.cvs.sourceforge.net:/cvsroot/courier co -P sysconftool
You can view a list of files or copy all the CVS repository data via rsync (the 1st command lists the files, the 2nd copies):
rsync -a a.cvs.sourceforge.net::cvsroot/courier/
rsync -ai a.cvs.sourceforge.net::cvsroot/courier/ /my/local/dest/dir/
If you are a project admin for courier, you can request that this page redirect to another repo on your project by submitting a support request.