Hotmail has stolen a rare lead on Google’s Gmail with a new security feature that lets webmail users create temporary email addresses which can later be discarded.

The new ‘aliases’ can be used to create up to five secondary email identities that link back to a user’s main email account as a way of interacting with online services on a temporary basis. Once the need for this relationship has ended, users can turn off or delete the alias to avoid receiving marketing or spam.

To ease management of the aliases, Hotmail can route mail from each into different folders or mark them using distinct symbols for simple identification.

“We’ve all been in a situation when we have to sign up for or buy something, like a car or a holiday, and provide our email address. Most likely, it’s something or somewhere we’re not likely to visit again anytime soon,” said Hotmail product manager, Bryan Saftler.

Saftler pointed out that email addresses are now used for more than simple messaging with select acquaintances, and now formed the frontline of many people’s digital identity. Managing this through one identify could be difficult, which encouraged some users to create multiple email accounts.

That’s where Hotmail wins. The company will, presumably, no longer have to manage large numbers of empty email accounts for people who only created them for a short-term reason. That means less hassle at its end.

The limitation is the five alias limit in any year, or 15 in total. No doubt this is to stop a minority of users – or spammers – going mad with the number of aliases that hang off one primary account.

As Microsoft worked out long ago, the bigger picture is identity itself.

The Internet is crying out for users to interact with a large number of services using broker services, which is where Windows Live ID and Google identities might in future come in. Users wouldn’t log in or exchange information with multiple sites but let brokers present the user data on a temporary basis that deletes traces when the transaction is finished.

This can already be done with Microsoft’s Passport Network or Windows Live ID but depends on that filtering down to larger numbers of sites, which it has yet to do. De facto identity companies such as Facebook now look more likely to steal this crown but Hotmail aliases might yet be a way for Microsoft to claw back some lost ground.