Which email security measure ensures that messages remain confidential during transmission?

Email encryption is the measure that ensures messages remain confidential during transmission. It works by converting the email content into a format that can only be read by someone who has the appropriate decryption key. This significantly protects sensitive information from being intercepted and accessed by unauthorized individuals while the email is being sent over the internet.

By encoding the message contents, email encryption prevents eavesdropping and ensures that even if the email is captured during transmission, it cannot be read without the specific decryption keys. This is particularly important for organizations handling sensitive data, as it helps to comply with privacy regulations and maintain the confidentiality of communications.

In contrast, spam filtering is primarily focused on reducing unwanted email, while two-factor authentication adds a layer of security to user accounts, and sender verification checks the authenticity of the email sender without encrypting the content of messages. These measures are valuable in their own right, but they do not specifically address the confidentiality of email messages during transmission like email encryption does.