Google has found a fix for a bug that affected Google Apps' Sync for Microsoft Outlook by preventing some emails from being downloaded from Gmail servers to the Outlook program on end-users' PCs.

Since users were unaware that not all their email messages were being replicated to Outlook, they often failed to respond in a timely manner to affected messages, according to problem reports posted to the Google Apps discussion forum.

Once aware of the bug, the affected users typically got into the habit of checking Gmail's web interface periodically to see if all inbound messages had reached their Outlook application.

Google started rolling out a patch to fix the problem and expects to finish in the coming days, a Google spokeswoman said. "Once the rollout is complete, we will re-download any missing messages to affected users," she said via email. "As we noted in the help center, the bug only affected a small number of messages for a very small number of users."

Since the patch will be applied to Google's Gmail servers, neither Apps administrators nor end-users need to take any action.

Google acknowledged the bug in the Google Apps discussion forum on March 12 and had promised a fix for early last week. In the forum, a Google representative said the bug was introduced via a software upgrade earlier in March, but some Apps administrators posted messages saying they've had the problem for longer.

According to Wesley's post, the bug "primarily" affects end-users who haven't downloaded messages to Outlook for several days straight, although some Apps administrators wrote in the forum that the bug has hit end-users who haven't let messages accumulate in Gmail.

Apps Sync for Microsoft Outlook, a free Outlook plug-in launched in June 2009, lets users of the Apps Premier and Education editions use Outlook as a front end to the server-side Gmail and Calendar components of the suite. The Premier edition costs $50 per user per year, while the Education edition is free.

At the launch of Apps Sync for Microsoft Outlook, Google positioned it as a key element for smoothing the migration of organizations from Exchange to Gmail by giving users the option of using Outlook if they prefer it to the Gmail web interface.