If you're having trouble with messages from a particular sender (or fitting some other grouping, like a common subject title) being incorrectly marked as spam, you can now prevent these from being sent to your spam filter in the future:
- Create a filter (you can do this while reading the message in question: click the down-arrow next to the Reply link, and select 'Filter messages like this' from the menu).
- Enter the information of the messages that are being improperly labeled as spam (e.g. the sender's email address).
- Click Next Step.
- Select the checkbox next to 'Never send it to Spam.'
From here on, no messages matching your filter criteria will be marked as spam. If you receive a message in your inbox that would have been marked as spam, but wasn't only because it matched your filter criteria, you'll see a yellow bar at the top of the message that says 'Due to a filter you created, this message was not sent to Spam.' If the message really was spam, you may want to edit your filters to make sure no more of the bad messages slip through the cracks.