Google's attempts to get Microsoft into trouble with the UK Advertising Standards Authority over its anti-Gmail advertising campaign have failed.
The Seattle-based company ran a series of adverts which attacked the privacy standards used by Google's Gmail email service to promote Microsoft Outlook.
The advert said that Gmail scanned the contents of users' emails for commercial purposes. Ironically, Microsoft was caught red-handed after it admitted reading a journalist's emails on Hotmail.
A radio advert said that Gmail users will have to adopt an indecipherable language, Pig Latin, if they want to stop Google from scanning their messages to glean personal information to sell to advertisers.
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The ad continues: "Pig Latin may be hard to understand, but you probably need it if you use Gmail, because Gmail scans every word of your emails to sell ads."
The Advertising Standards Authority received two complaints challenging whether the ad was misleading because they believed that Microsoft was no better and also scanned the contents of the all emails.
However Redmond said that Outlook.com offered greater privacy options than Gmail, arguing that it only undertook "protective" scanning of emails for viruses and spam.
The ASA agreed it was "standard practice" for email providers to scan for viruses and spam, while the criticism of Google's Gmail related to scanning email contents to target ads.
"Because the ad made clear that the privacy claims were in relation to ad targeting, which Outlook.com does not carry out, we therefore concluded that the ad was not misleading," said the ASA.
As a result, the ASA said that Microsoft's claims did not breach UK rules relating to misleading advertising.