Which version of procmail should I get

Smartlist README says that smartlist files have to be unpacked in the procmail source directory. The latest procmail version is 3.15 and the latest smartlist version is 3.13. Smartlist untars into procmail-3.13 directory while procmail upacks into 3.15 directory. My question is, which version of procmail should I get to make sure it is compatible with the latest smartlist? I would like to use the latest procmail version if possible. Thanks. Akop