Customers who have regularly paid to use Adobe's Photoshop software have been politely threatened with litigation for using older versions.

After discontinuing older versions of the popular photo editing software, Adobe emailed customers regarding its policy towards users who don't abide the company's rules.

'We have recently discontinued certain older versions of Creative Cloud applications and and a result, under the terms of our agreement, you are no longer licensed to use them,' Adobe said in the email.

'Please be aware that should you continue to use the discontinued version(s), you may be at risk of potential claims of infringement by third parties.'