With glibc 2.3.5 in unstable we have again reached the point in time which makes it unwise to install (almost all) packages from unstable on a stable system, as upgrading libc6 to unstable would be necessary, too. This should soon trigger a strong interest in backports for sarge, I guess a sarge directory will soon appear on backports.org.
As early adopter (and to force me to actually test my packages) I have
again started to provide backports of
exim4.
Feel free to add
deb http://www.bebt.de/debian/ sarge exim4
to your sources.list. Sources are available on the same site, just
replace deb with deb-src. - The interdiff to unstable's 4.52-2 only
consists of a one-line-patch to debian/control, downgrading the
Build-Depends.