www traffic is typically initiated from a host on the pix inside. It has destination port 80 but the source port is most often not 80. Return traffic from the internet will therefore not be on port 80 either.
Your webmailserver should also run as www-proxy when you want to send www traffic over it. Then redirect your clients to use this proxy and block all other inside IP's for NAT.
assuming only 1 public ip is available, and which has been shared by the pix outside interface, the webmail server, this particular pix will not be able to forward port 80 traffic again to another server.
one way is to re-configure the mailserver webmail service listening port, and then create another static and inbound acl.
e.g. if the webmail is now listening to port 8080, then:
no static (inside,outside) tcp interface www WEBMAILSRV www netmask 255.255.255.255
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...