New European laws came into effect on Thursday.

Spam can be sent only if the recipient has agreed in advance to accept it.

Firms which flout the law could be fined up to �5,000.

But this won't mean an instant end to overflowing mailboxes - much spam is sent from outside the European Union, so does not come under the legislation.

"They won't necessarily catch hardcore spammers who are based outside Europe peddling illegal or disreputable products," says Nick Graham of law firm Denton Wilde Sapte.

Hampered

"This kind of hardcore spammer didn't pay much attention to rules in force before these new rules, so individuals with Hotmail accounts will have to look at more practical, homegrown ways of solving the problem."

It's estimated that spam now accounts for 50% of global e-mail traffic, compared with just 8% two years ago.

But there have been concerns that businesses could be hampered if they are not allowed to market themselves and their products by e-mail.

There is a limited exemption so they can keep contacting existing customers about similar products and services.

Companies or individuals that break the laws can be reported to the office of the Information Commissioner, which has the power to take them to court.