[Drupal] How can we send mails in Drupal 6 with attachments?

While working on a Drupal 6 project, I came across the requirement to send some mails. Interestingly, I couldn't find any good articles or procedures on the same. So, here, I am going to explain how to send mails in Drupal 6 with attachments. If you need any business support, get in touch immediately.