Alternatives to OWA for Exchange 5.5 dial-up clients to minimize open firewall ports
Are there any other alternatives to using Outlook Web Access for Exchange 5.5 dial-up clients, in order to minimize the number of firewall ports that have to be opened?
OWA uses TCP Port 80 for HTTP and TCP Port 443 for HTTPS requests, so you only need to open one of these ports (preferably 443 so that you can use SSL in your remote OWA implementation). Alternatives to OWA include POP3 and IMAP4, but those will also require you to open up the proper port.
You might also just look into a VPN/Terminal Services solution. If you use VPN, you only need one port open no matter what you are doing. Once your dial-up clients have a VPN connection, they can use Terminal Services (or the Terminal Services Advanced Client) and get the benefit of using a full MAPI client, or still use OWA, depending on your needs.
This was first published in March 2002