“Hotmail: Free, trusted and rich email service. Get it now.”

When Hotmail launched in 1996 it grew fast. Very fast. It was one of the first free webmail providers, and they had a killer marketing idea – add a tagline at the end of every single email sent from hotmail to promote the service. Every time you sent an email you were spreading a marketing message virally.

That led to a $400 million acquisition by Microsoft and the beginning of the “viral” age on the Internet. There wasn’t a business plan put in front of a venture capitalist for years that didn’t have a slide or two on how their product would spread virally via its users.

Today Hotmail will finally kill off the tagline. “We want to start respecting the inbox” Brian Hall, Microsoft’s general manager of the Windows Live Business Group, told me yesterday. He says it’s still a great way to get new users. “But some people don’t think it’s professional,” he says.

Hall also says that Microsoft will cut back on the number of marketing messages they send to Hotmail users. In fact, if users aren’t opening those emails, Hall says they’ll stop sending them entirely. Users can also choose to have all emails stopped as well. When asked why they send them at all, he said that some users actually seem to like them and use them to discover new products and services at Microsoft