List of versions/pkgsrc equivalent options of things in base

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

There is number of programs like postfix which are included in the  
base system but have more recent versions available via pkgsrc. Also,  
via pkgsrc, they can be built with options not enabled in the version  
present in base.
Is there a list of such programs, including the version shipped with  
base and something equivalent to the pkgsrc options the base versions  
were built with?
I would like to have a means to, given a demand like "postfix >=2.2",  
automatically decide that the base version is good enough, or, given  
"postfix with sasl enabled", decide to try the pkgsrc version.