No one can answer that without knowing what email system you use. But if your spam filter is adaptive, it'll learn eventually if you mark incorrectly categorized emails as "spam" or "not spam".
While we're on the subject of Craigslist and email, it's a bad idea to depend on CL's built-in email response system. Their spam filtering is way too rabid, and rejects emails from around 1/3 of users. So if you want replies from that 1/3 of potential buyers, make sure to put an email and/or phone number in your post.
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