legit email is being marked as spam by Cox filter and hidden in webmail spam folder.

When I mark it as "Not spam" and it is delivered to my inbox, I can't reply to the sender because your filter still thinks it is spam. I can't even send a new message to this store about an order because your filter says it is spam.  But you let their marketing emails through with no problem.  In fact, you let tons of spam and phishing emails go straight to my inbox and block even more legit messages.  What is wrong with Cox?