[QSTR]

Hehe. Enjoy!

Here is the version with mail subject to post title.
No subject, no title.

Should work for iso-8859-1 etc.
For UTF-8 you will have to make some tweaks.

PHP Code:

<?php
    // simple email2post
    // fix it as you need

    // QSTR - 17.05.2015r1
    // https://vborg.vbsupport.ru/showthread.php?t=318396
    // GPL - http://www.gnu.org/copyleft/gpl.html

    require_once('./global.php');
    require_once(DIR . '/includes/functions_databuild.php');

    // configure as you need
    // http://php.net/manual/en/function.imap-open.php
    $imap = imap_open("{localhost:995/pop3/ssl/novalidate-cert}INBOX", "user", "pass");

    // user id used for posting
    $post_user_id = 1234;

    // forum id
    $post_forum_id = 1;

    // thread id
    $post_thread_id = 1;

    #######################################################################################################################

    // add post, simple
    function add_post($userid, $post, $post_title, $forumid, $threadid, $timestamp)
    {
        global $vbulletin;

        // setup datamanager
        $tdm =& datamanager_init('Post', $vbulletin, ERRTYPE_ARRAY, 'threadpost');
        $tdm->set('userid', $userid);
        $tdm->set('pagetext', $post);
        $tdm->set('allowsmilie', 1);
        $tdm->set('visible', 1);
        $tdm->set('threadid', $threadid);
        $tdm->set('dateline', $timestamp);

        // if set
        if ($post_title && trim($post_title) != "")
        {
            $tdm->set('title', $post_title);
        }

        // try to save the post
        $tdm->pre_save();

        // check for errors 
        if (empty($tdm->errors))
        {
            $post_id = $tdm->save();

            // rebuild counters
            build_thread_counters($threadid);
            build_forum_counters($forumid);

            return $post_id;
        } else {
            return false;
        }
    }

    // connection ok?
    if ($imap) 
    {
        // count the messages in the mailbox
        $mails_count = imap_num_msg($imap);

        // if we got some
        if($mails_count > 0) 
        {
            // each mail
            for ($mail_id = 1; $mail_id <= $mails_count; $mail_id++)
            {
                // mail header
                $mail_header = imap_headerinfo($imap, $mail_id);
            
                // mail body
                $mail_body = imap_qprint(imap_body($imap, $mail_id));

                // mail subject
                $mail_subject = $mail_header->subject;
    
                // some info
                echo $mail_id . ".<br>";
                echo "subject: " . $mail_subject . "<br>";
                echo "mail body: " . "<br><pre>" . $mail_body . "</pre><br><b>post id: ";
                echo add_post($post_user_id, $mail_body, $mail_subject, $post_forum_id, $post_thread_id, time());
                echo "</b><br><hr><br>";

                // mark for deletion
                imap_delete($imap, $mail_id);
            }
        } else {
            echo "empty mailbox";
        }

        // delete marked messages, close imap
        imap_expunge($imap);
        imap_close($imap);
    } 
?>