However, there is a solution! By adding a simple mail rule, you can continue to set "Move it to the junk mailbox" in Mail's preferences, but have Mail ignore messages in GMail that it thinks are spam. First, make sure that, in Mail's preferences on the Junk Mail tab, Filter junk mail before applying my rules is unticked. Without this, the rule won't be applied. Now, add a new rule that says:
If all of the following conditions are met:
- Message is Junk Mail
- Account: GMail
- Stop evaluating rules

