Yahoo error code 475 means that Yahoo catched some suspicious or doubtful activity on an account and is temporarily blocked users from sending emails. There are many things that lead to the Yahoo mail error code 475. Here is the list of reasons that lead to the error.
1. When Yahoo users send a lot of emails in a short time.
2. When sending duplicate info repeatedly.
3. Due to sending repetitive messages to your Yahoo contacts.
4. When a message is stuck in the Outbox folder of your Yahoo Mail app.