The update is the first Universal application launched by Microsoft for Intel-based Macs, the company said. In Apple's lexicon, "Universal" indicates that an application runs on both PowerPC- and Intel-based Macintosh computers.
Other improvements in version 6 include built-in spell checking, custom-made emoticons, and iTunes sharing.
Microsoft also pointed out that as of Wednesday, all Mac Messenger and Windows Live Messenger users can access friends who use the rival Yahoo Messenger. Although the two companies announced that they would integrate their IM networks last year, it was only in July that they began interoperability beta testing. Together, Microsoft and Yahoo boast a slightly larger pool of users than the 47 million who rely on AOL's instant messenger software.
Mac users, however, were not impressed by the update. Several reported problems using the new client on Microsoft's own newsgroup, while others on BetaNews trashed the application.
"Terrible release! Seems like this is a desperate release to keep the Mac community at bay again," wrote a user identified as "FrequentFlyer."
Mac Messenger 6.0 requires Mac OS X 10.3.9 or later, and is available for downloading from Microsoft's Mactopia Web site.