If your sig is up to date: Autoquote is an option under tools menu BUT it appears only when replying - UT reasoning for this, is that it is a feature of replying - of course, because of this logic, first time you set it 'on' you don't get the autoquote.
I think it should be always under Tools, not only when replying, and it should also be part of the account setting.
OTOH, many times autoquote is a waste of resources - some members are part of 'autotrim your reply' campaign...