AOL - for the first time - is serving up ads in its paying customers' email messages, in an effort to increase online ad inventory, writes PC World. AOL surveyed subscribers and ran a test, and concluded that the banner ads in AOL Mail messages would not unduly upset subscribers, according to an AOL spokesperson.

The banner ads are being shown to AOL subscribers using version 9.0 of the company's proprietary software. The ads are not being targeted based on email content. The move is consistent with AOL's recent push to generate more revenue from online advertising.

AOL has displayed banners on the main AOL Mail inbox for several years - but not within email messages themselves. Apparently, that policy changed a few weeks ago.