What common feature do many email clients provide to enhance SMTP usage?

Many email clients provide the option to encrypt emails as a common feature to enhance SMTP usage. Email encryption is vital for ensuring the security and confidentiality of messages while they are transmitted over the internet. By encrypting emails, users can protect sensitive information from unauthorized access, as only intended recipients with the correct decryption keys can read the contents. This security measure is particularly important in an era where data breaches and privacy concerns are prevalent.

While other features like spam filters, email template creation tools, and sender authentication protocols also play important roles in improving email functionality and security, they do not directly relate to the core enhancement of SMTP usage in terms of securing message content during transmission. Encryption specifically addresses the integrity and confidentiality of the data being sent, which is essential in the context of email communication.