Здравствуйте. В Squid3 ето не помагает.
acl SSL_ports port 995 # POP3
acl SSL_ports port 993 # IMAP
cl SSL_ports port 456 #SMTP
# Deny requests to unknown ports
http_access deny !Safe_ports
# Deny CONNECT to other than SSL ports
http_access deny CONNECT !SSL_ports