In general, I grab my sources from ftp.uu.net and the other fine archive sites on Internet. In addition, Linux-specific binary ports are found in the usual Linux distrbutions and on the usual Linux anonymous ftp sites (sunsite.unc.edu and tsx-11.mit.edu in particular).
The newspak-2.1.tar.z distribution contains config files and readme files related to building uucp, news, and mail software under Linux from the various freely-available sources. It can usually be found on sunsite.unc.edu in the directory /pub/Linux/system/Mail.