I always wondered the maximum number of threads Gmail can handle in a single conversation. Today I reached the maximum capacity. The maximum is 100. After this even though you can reply, the message doesn’t submit. Gmail says that is submits the message. But the thread doesn’t update. Interesting indeed.
UPDATE : So within the course of the day I learnt that actually the message I sent after the 100th message did submit, and that GMail had created a newer thread with the same recipients and subject. Quite neat.