Many email campaigns work well at first, then suddenly start landing in spam folders. This usually happens when email services like Gmail or Outlook begin to think the messages look suspicious. One common reason is sending too many emails in a short time, which can look like spam activity. Another reason is low engagement. If many people delete the email without opening it, the system assumes the content is not wanted. Poor subject lines, too many links, or spam-like words can also cause problems. What do others think usually causes this situation?