Allowing Outllook express through squid

Hi,
I Have recently installed Squid Proxy 2.6 on my linux server for a cleint which is a school. I put Squid on so as to keep internet access secure for the pupils and to be able to control what is accessed. Squid is working well but I have come accross a problem now in that staff cannot recieve emails on their laptops and we cant update virus software etc. Is there someway we can at least unblock the pop3 and smtp ports (110 and 25) using an acl or something like that? If you need more information send a message back or contact me off list.
Any suggestions would be appreciated. thanx 😀