Sent mails with phpmailer don't go to "Sent" IMAP folder

I found easier way to do this. PHPmailer prepares email as string - all You have to do is to put it into right IMAP folder.

I expanded phpmailer class with this code (since vars are protected I can't reach them):

class PHPMailer_mine extends PHPMailer {
public function get_mail_string() {
    return $this->MIMEHeader.$this->MIMEBody;
}}

PHP code:

$mail= new PHPMailer_mine();
//code to handle phpmailer
$result=$mail->Send();
if ($result) {
    $mail_string=$mail->get_mail_string();
    imap_append($ImapStream, $folder, $mail_string, "\\Seen");
}

It works well.

There is now a method getSentMIMEMessage in PHPMailer which returns the whole MIME string

$mail = new PHPMailer();
//code to handle phpmailer
$result = $mail->Send();
if ($result) {
  $mail_string = $mail->getSentMIMEMessage();
  imap_append($ImapStream, $folder, $mail_string, "\\Seen");
}

Well, it's pretty difficult, but can be done.

Take a look at the imap-append function.
By being connected to an IMAP stream resource, you can use the imap-append() to append your mails to the Sent folder of your IMAP account.

But reading through the comments will show you that it's a bit tedious to accomplish, but certainly not impossible - you'll probably need to code something on your own, since phpmailer doesn't support this out of the box (and will most likely be too time consuming to implement instead of making something yourself).