More than a decade and a half after it was first introduced, Hotmail is officially no more.

In a blog post yesterday, Microsoft announced it had completed the upgrade of hundreds of millions of users from the old Hotmail platform to the new Outlook.com – a process, according to Microsoft, that involved transferring 150 million gigabytes of data. Hotmail account holders will be able to keep their old Hotmail address, and all settings on Hotmail mobile and Web applications will automatically be updated.

The jettisoning of Hotmail – and the introduction of the sleek, shiny Outlook.com – is an effort to bring Microsoft's mail service up to date with the Windows 8 operating system.

Naturally, though, the move hasn't made everyone happy. Some users have circulated petitions asking Microsoft to preserve Hotmail; others have created Facebook pages or taken to Microsoft forums to express their frustrations. ("The forced 'upgrades' have begun," one forum-goer recently wrote. "But I simply will not lie down and say, 'Yes, Microsoft, I like this because you tell me I should.' ")

In a blog post yesterday, Microsoft's Dick Craddock acknowledged that when any "widely-used consumer service makes any substantial change," people are going to kick up a fuss. But Mr. Craddock urged users to give the new Outlook a chance.

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"It's gratifying in a sense because it means those customers loved the previous set of changes we made," he wrote. "With a communication service that is constantly evolving, we try to strike the right balance between bringing out major improvements and keeping true to what our customers love. Our belief is that as people start using the new experience, they will come to love it even more than they loved Hotmail."

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