Are there any websites that allow standard correspondence chess time controls? I noticed that most websites that allow correspondence chess have time controls that are per move. I believe that historically correspondence chess was played with x days per y moves, which allows one to distribute time where it is needed most, while not making games excessively lengthy, and taking into account the length of a game. As far as I know, official international correspondence chess tournaments are still played this way. 

Are there any free online websites that allow this, even if only to set up opponents who can play via e-mail (maintaining a ratings system)? If there are no free sites, what are the non-free options? 

An answer to this question Best websites for correspondence chess? listed 5 sites, but I checked all of those and none of them seem to allow standard time controls.
http://ChessTempo.com offers a wide choice of correspondence time controls including a fixed number of days per game, or increment after a move. Just check it out.