AOL has partnered with Plaxo to make it easier for AOL email users to keep the contact information in their address books updated, the companies announced this week.

The technology integration will benefit users of AOL Mail, which is the email service for AOL subscribers, and AIM Mail, which is the web mail service of AOL's instant messaging service.

The Plaxo functionality will become available in a test, or beta, release in October.

It will allow users to synchronise their AOL Mail and AIM Mail address-book information with web-based address books from various providers and with Microsoft's Outlook and Outlook Express. AIM users will also be able to pull AIM contact information from address books to add to their Buddy List.

Additionally, AIM presence information will become visible from within the Plaxo service and Plaxo-enabled applications such as Outlook and Outlook Express.

Plaxo provides "looser" integration with competing web mail services from Microsoft and Yahoo.

For example, Plaxo offers a toolbar for the Internet Explorer browser that lets users engage in two-way synchronisation of the Plaxo and Yahoo address books. Meanwhile, Plaxo can pull data from Microsoft's Hotmail address book, but not send data back to it. Plaxo does not have integration with the instant messaging services from Yahoo and Microsoft.

Although the integration initiative with AOL isn't exclusive, it is "the most significant project [of this kind] we have right now" and is "far and above" what Plaxo has with other web mail providers, such as Yahoo and Microsoft, says Ben Golub, Plaxo's president and chief executive officer.

AIM Mail, launched in June, already has over 1m users.

Neither AOL nor Plaxo will charge for the features being added to their respective products.