The shutdown lasted for less than an hour during midmorning PT, according to the Microsoft representative.
As of this morning, people trying to enter their Hotmail accounts were greeted by a message informing them of the problem.
"We apologize, but your account is temporarily unavailable. This delay does not affect the entire site or relate specifically to your account, but the machine that holds your account information is temporarily unavailable," part of the message read.
Hotmail is not the only free email provider to suffer from malicious account-stealing exploits recently. Yesterday, Yahoo, Excite@Home and USA.net implemented safeguards against a password-stealing exploit, in which a malicious email sender could lead account holders to a bogus but convincing password-entry screen.
The Microsoft representative said that the exploit affecting Yahoo yesterday was not related to today's Hotmail incident.
The outage also comes a few weeks after Microsoft patched a password-stealing bug in Hotmail.