Is it necessary to include both IsHTML and IsSMTP functions when sending emails with PHP mailer?

It is not necessary to include both IsHTML and IsSMTP functions when sending emails with PHP mailer. IsHTML is used to set the email content type as HTML, while IsSMTP is used to send emails using SMTP. If you are sending HTML emails using SMTP, you can include both functions. However, if you are sending plain text emails using SMTP, you only need to include IsSMTP.

// Example of sending HTML email using SMTP
$mail = new PHPMailer(true);
$mail->IsSMTP();
$mail->IsHTML(true);
// additional code for SMTP settings and email content

// Example of sending plain text email using SMTP
$mail = new PHPMailer(true);
$mail->IsSMTP();
// additional code for SMTP settings and email content