Microsoft said it is beefing up security in an upcoming version of its Windows Live Hotmail service.
Volish anti-spam and anti-phishing chief John Scarrow said security is the "number one concern of people who use email and a top priority for all Microsoft development efforts, products, and services – Hotmail included."
The new Hotmail will allow users to use a registered mobile phone to prove their identity when trying to access their account from public computers, "such as those found in Internet cafés, airports, and coffee shops".
"When you request a single-use code, the code is sent via SMS to the phone number associated with your Windows Live ID. It acts as a one-time substitute for your password," Scarrow blogged. "By using a single-use code, you won't have to type your password into a public computer."
Mobile phone messages may also be used when a user forgets their password or has their account compromised. An account recapture code can be sent via SMS and used to regain access to their account.
Scarrow says the option should help prevent passwords "from being stolen by key loggers and the like."
The new Hotmail will support the option to maintain an SSL-encrypted connection for a the entire online session. Microsoft said it will also introduce "safety logos" which will be displayed next to messages from those trusted senders, such as banks, which Microsoft confirms as legitimate.
The improved Hotmail will launch "later this summer".