What are the main differences between sendmail and qmail in terms of email handling in PHP?

Sendmail and qmail are both Mail Transfer Agents (MTAs) used for sending emails in PHP. The main differences between the two lie in their architecture and configuration options. Sendmail is a more traditional MTA with a complex configuration file, while qmail is known for its simplicity and security features. To switch from using sendmail to qmail in PHP, you will need to update the mail configuration settings in your PHP code to point to the qmail binary instead of sendmail.

// Set the path to the qmail binary
ini_set('sendmail_path', '/var/qmail/bin/qmail-inject');