Strange behavior with imap, php and apache

I just installed Red Hat 7.3 with Apache and PHP. I ran a simple script to test the imap_open function and it doesn't work when using the values for servers on my subnet. http://www.gym.itesm.mx/imap.php However, if the mailbox I request to open is on another server outside, it does work. The strange thing is that a friend of mine has the same script running on his server (http://pollux.icon.net.mx/~antonio/imap.php) and he can read a mailbox from my subnet as well as any other. When I run the script on my server and try to access a local mailbox I get the following error: Warning: Couldn't open stream {www.gym.itesm.mx:143}INBOX in /home/campus/html/imap.php on line 5 I just don't know what could be wrong. Help is appreciated. The script I'm using (comments added to avoid html rendering): // <?php // // function test_imap($mbx,$uid,$pwd) // { // if (!$mbox = imap_open ($mbx, $uid, $pwd)) // { // echo "<br /><br />"; // echo "<span style='font size: x-large;color:red;'>Password incorrecto</span>"; // echo "<br /><br />"; // echo "<pre>"; // echo "<b>Mailbox.:</b> $mbx<br />"; // echo "<b>Cuenta..:</b> $uid<br />"; // echo "<b>Password:</b> $pwd<br />"; // echo "<b>Error...:</b> "; echo imap_last_error(); // echo "</pre>"; // } else { // echo "Password correcto: $mbx"; // imap_close($mbox); // } // } // // if (!isset($mbx1)) $mbx1 = "{www.gym.itesm.mx:143}INBOX"; // if (!isset($uid1)) $uid1 = "gsoberon"; // if (!isset($pwd1)) $pwd1 = "mypass"; // // if (isset($test)) { // test_imap($mbx1,$uid1,$pwd1); // } // // ?> // <html> // <body> // <hr> // <form action="imap.php" method="get"> // <p> // mailbox: <input type=text name=mbx1 value="<?echo $mbx1;?>"><br /> // usuario: <input type=text name=uid1 value="<?echo $uid1;?>"><br /> // passwd: <input type=text name=pwd1 value="<?echo $pwd1;?>"><br /> // <br /> // <input type=submit name="test" value="Test"> // </p> // </form> // </body> // </html> -- Sergio Tirado