A mail is a PAD template, rendered to an HTML part and a text part and handed to a transport. Templates live in _mail/, looked up like _include/: _mail/welcome.pad is the HTML part, _mail/welcome.txt the text part - without one, the text is made from the HTML - and _mail/welcome.php runs first. _inits.pad and _exits.pad in the same _mail/ are the email's layout, with @page@ where the mail goes:

<?php

  padMail ( 'ann@example.com', 'welcome', 'Welcome to the shop', [ 'name' => 'Ann' ] );

  $mail = $padMailLast;

?>

<p>To {$mail.to}: <b>{$mail.subject}</b></p>
{$mail.text}
{!mail.html}

Welcome, Ann!

Your account is ready: sign in (https://example.com/account).

-- The shop

From a template, {mail} sends the same way. With a template it is {mail to=$email, template='welcome', subject='Welcome'}; as a pair, the content is the HTML part, rendered where it stands - in a loop with the fields of the row:

<?php

  $name = 'Ann';

?>

{mail to='ann@example.com', subject='Your order'}
  <p>Thank you for your order, {$name}.</p>
{/mail}
<p>Sent: {$padMailLast.subject}</p>

• from, cc, bcc and replyTo set the other headers; an address is ann@example.com or Ann <ann@example.com>, several separated by commas. A line break in any of them is refused.
• $padMailTransport says where it goes. 'file', the default, writes every message as an .eml under DATA/mail/ instead of sending it, keeping the newest $padMailKeep; 'mail' sends through PHP's mail(); the name of a function of the application gets the message - the place for SMTP through a library.
• $padMailFrom is the sender; $padMailLast the last message of the request.