According to the developer, swiftmailer cannot copy to Sent folder because it is a mail sender and not mailbox manager.
As mentioned on the github page:
Swiftmailer is a library to send emails, not to manage mailboxes. So, this is indeed out of the scope of Swiftmailer.
However, someone from php.net posted a solution that might work for you:
Use SwiftMailer to send the message via PHP.
$message = Swift_Message::newInstance("Subject goes here"); // (then add from, to, body, attachments etc) $result = $mailer->send($message);
When you construct the message in step 1) above save it to a variable as follows:
$msg = $message->toString(); // (this creates the full MIME message required for imap_append()!! // After this you can call imap_append like this: imap_append($imap_conn,$mail_box,$msg."\r\n","\\Seen");