get-email-addresses-from-imap.php

<?php

$login = 'someone@somedomain.com';
$password = 'theirpassword';
$server = '{mail.someimapserver.com:143}INBOX.Sent';

$mbox = imap_open($server, $login, $password);

$n_msgs = imap_num_msg($mbox);

$emails = array();

for ($i=0; $i<$n_msgs; $i++) {
    $header = imap_header($mbox, $i);
    $to = strtolower($header->to[0]->mailbox.'@'.$header->to[0]->host);

    if (!in_array($to, $emails)) {
        $emails[] = $to;
        echo $to."\n";
    }
}

imap_close($mbox);