Control your users and data (Score 1)

For an ISP, it's important to retain your customers and provide them a reliable email-service and Webmail interface.

Just passing on this critical part of an ISP to a big player like google, waters down your ISP offerings and you loose control over your customers, the ability to charge for added services, and not to mention the security.

Do you really trust moving all your customer emails to google? When customer xyz calls up about their email, do you really want to tell them to call google because as the ISP you have no control?

Just as Google sees the value in retaining customers, email, data, power, so should you as an ISP.

We develop Email-server & Webmail solutions based on Linux called @Mail, and have a lot of experience consulting ISP's in this area.