What are the potential pitfalls or security concerns when implementing email send/read receipts in PHP?

Potential pitfalls or security concerns when implementing email send/read receipts in PHP include the risk of exposing sensitive information such as email addresses or tracking user activity without their consent. To mitigate these risks, it is important to ensure that the implementation complies with privacy regulations and obtain explicit consent from users before sending or tracking read receipts.

// Example of obtaining user consent before sending read receipt
if ($userConsent) {
    // Code to send email with read receipt
} else {
    // Code to handle user not consenting to read receipt
}