Laptop mobile users cannot use their home SMTP server.
Depends on the configuration of the SMTP server and the mail server & client running on the laptop. With SMTPAUTH and/or TLSSMTP, and using a different (unfiltered) port, this shouldn't be a problem.
1. The basic issue is with control over outbound ports. Whatever hacks might deal with the particular details of problems in blocking outbound port 25, the problem resurfaces for other ports. For example, I have been in a number of installations that block all but a few outbound ports, so that even non-25 email is not accessible. It is the philosophy of blocking outbound ports that is the real mistake.
2. The issue with email is authentication, not privacy. Authentication can be achieved can be achieved easily over port 25, without encryption. Hence, blocking port 25 blocks legitimately validated email, as well as possible spam.
In other words, by blocking output SMTP, mobile users are hurt badly.
Can be. Yup. Think of all the iPass and GRiC customers who don't even know who the local provider is that they're dialing up, so that they can get a network connection?
Exactly correct. And all the people who visit an organization and use their LAN access. And all the people who visit 802.11 hotspots.
I know that *I* certainly am. Constantly and serously.
I'm very sorry to hear this. Maybe we can help you get SMTPAUTH and/or TLSSMTP set up on your server and/or client?
SMTPAUTH works over port 25.