Joshua Trutwin wrote on Wed, 6 Apr 2011 14:52:23 +0000:
Some clients also thread by subject by default, I usually use claws mail for ML stuff as it's threading is excellent.
Threading by subject works only in small threads with few people. The client doesn't know to which message the reply belongs, only to which thread, so it's got to use date or incoming date for threading.
Kai