Research by the discount code website revealed that just 19 percent of men would ditch their girlfriend for the same crime.
Furthermore, 22 percent of women would dump a man for following TV presenter Vernon Kay's lead and sending sexually explicit messages to other women on micro-blogging service Twitter. Only 17 percent of men said it would do the same.
When it comes to sending a saucy text message, 71 percent of Brits admitted this qualified as cheating.
However, MyVoucherCodes revealed Brits think flirting over email is worse than sending saucy text messages or explicit messages of Twitter.
A quarter of women said they'd dump a boyfriend for sending saucy emails to a colleague, while a third of men would dump a woman for the same offence.
Furthermore, 10 percent of men said they suspected their partner was flirting with a male colleague on email, but only a quarter found this to be true.
"I'm not too sure why flirting by emails is considered more of a threat than via social networking or text," said Mark Pearson, managing director of MyVoucherCodes.co.uk
"Social networking and texts it can seem more open and obvious, while emails tend to be more personal. I think that with work emails, there may be a slightly higher sense of paranoia as there is that whole issue around people cheating with work colleagues."
See also: 20% of divorces mention Facebook