Comment 12 for bug 731752

mere user writes:

> I did notice that unrelated messages are treated as a single thread:
> say I have several independent message months apart, that just happen
> to have a common subject ("lunch"), but are not part of the same
> conversation and not even with the same correspondents, then they seem
> to be treated as a single thread. perhaps that's intended, though. E

Hmm, if you are only noticing it now, that means that the threading is
working a lot more effectively now than it did in the past.

You could set vm-thread-using-subject to nil, as Arik mentioned. Or,
you can have more fun by using thread folding, which will hide all the
old junk, while still telling you that it is there. To enable it, set
vm-summary-enable-thread-folding to t.

Cheers,
Uday