Aqui:
http://www.php.net/manual/es/ref.imap.php
está este ejemplo:
Código PHP:
<HTML>
<HEAD>
<TITLE>imap_check</TITLE>
</HEAD>
<BODY>
<?
//check for new messages
$mailbox = imap_open("{localhost/pop3:110}INBOX",
"#username#","#password#");
// Check messages
$check = imap_check($mailbox);
print("<PRE>");
print("Date most recent message : " . $check->Date);
print("<BR>");
print("Connection type : " . $check->Driver);
print("<BR>");
print("Name of the mailbox : " . $check->Mailbox);
print("<BR>");
print("Number of messages : " . $check->Nmsgs);
print("<BR>");
print("Number of recent messages : " . $check->Recent);
print("<BR>");
print("</PRE>");
// show headers for messages
$index=1;
$header = imap_header($mailbox, $index);
print("<PRE>");
print("Header Date : " . $header->Date . "<BR>");
print("Header To : " . $header->to) . "<BR>";
print("Header From : " . $header->From . "<BR>");
print("Header cc : " . $header->cc . "<BR>");
print("Header ReplyTo : " . $header->ReplyTo . "<BR>");
print("Header Subject : " . $header->Subject . "<BR></PRE>");
print("<PRE>");
print(imap_body($mailbox,$index));
print("</PRE><HR>");
imap_close($mailbox);
?>
</BODY>
</HTML>
Solo cambias esta linea a tu conveniencia:
$mailbox = imap_open("{localhost/pop3:110}INBOX",
"#username#","#password#");