function save_mail($pmail)
{
//You can change 'Sent Mail' to any other folder or tag
$path = "{outlook.office365.com:993/ssl}Sent Items.Subfolder";

//Tell your server to open an IMAP connection using the same username and password as you used for SMTP
$imapStream = imap_open($path, $pmail->Username, $pmail->Password);

$result = imap_append($imapStream, $path, $pmail->getSentMIMEMessage());
imap_close($imapStream);
}

"{outlook.office365.com:993/imap/ssl/novalidate-cert}Sent Items/Subfolder";
"{outlook.office365.com}Another Folder";
"{outlook.office365.com:993/imap/ssl}Sent Items.Subfolder";
"{outlook.office365.com:993/imap/ssl}INBOX";