Security experts have warned users to be on their guard against a "too good to be true" email that claims to come from Marks & Spencer.
The bogus message promises £100 worth of M&S vouchers in return for forwarding the message to at least eight people, and copying in a legitimate email address at Persimmon Homes.
However, neither M&S nor Persimmon Homes have endorsed the email and both companies advise recipients to delete it immediately.
"This email is 100 per cent phoney but unfortunately it is fooling users because it seems plausible given the growing trend for companies, such as Threshers, to make offers via email," said Graham Cluley, senior technology consultant at Sophos.
"I would advise users intent on sharing these chain emails to check the website of the company apparently making the offer to determine its authenticity before deciding to click the 'forward' button."
Persimmon Homes has published an advisory on its website informing users that the email is a hoax, and requesting that they do not forward it to friends, family and colleagues.
"Hoaxes of this nature may appear harmless but they can waste valuable bandwidth, affect staff productivity and place email addresses into the wrong hands," warned Cluley.
"Email spreads like wildfire and forwarding one copy could result in 100 more being sent, some of which could potentially reach cyber-criminals.
"If you receive an email that appears too good to be true, it probably is. Hit the delete button straight away to save any hassle down the line."
With £6.7m in initial funding, Mosa Meat could be the first company to offer lab-grown meat to the public
Manufacturing and finance jobs will be hit, but health and education can look forward to job creation, says PwC
US startups plan to modify existing jet engines, but are likely to fall foul of environmental legislation
The Brexit white paper "gets pretty close" to company desires, but there's still work to do