Microsoft late on Friday released an update to Outlook 2007 designed to speed up the communication software's much-criticized sluggishness.

The 8.3 MB update should accelerate the download of messages from the Exchange e-mail server and reduce temporary freezes resulting from deleting messages or copying them from one folder to another, according to Jessica Arnold, Outlook's program manager.

The update should also let Outlook 2007 users switch between messages faster and enable faster program startup, she said.

"I can't say that this will 100 percent solve the latency issues, but users should see a big improvement," Arnold said.

Complaints about Outlook 2007's tendency to freeze while executing tasks -- sometimes causing users to lose characters if they type too quickly -- began appearing on blogs and forums even before the software's release in November.

Most of the problems don't appear to be the result of underpowered PCs or of faulty or misconfigured e-mail servers. Rather, the problems are mostly due to changes made under Outlook's hood to accommodate new features such as RSS feeds and indexing for faster searches.

For instance, RSS newsfeeds are now downloaded and stored in users' local databases as .PST files. The files, which also store e-mails and calendar data, can quickly swell to several gigabytes in size for some users, making them very slow to read or write to, Arnold said.

Meanwhile, Outlook 2007's indexing of e-mails, while allowing for near-instant search results, can also cause delays even when run in the background.

Arnold said that while Microsoft had started hearing about problems even before Outlook's release to businesses last November, "until we had enough users, the data wasn't clear."

In addition to releasing its patch, Microsoft has updated its list of recommendations, first put out several months ago, on how to fix Outlook performance issues. They include taking older e-mails from an active .PST file and storing them in an archived .PST file.

Users who download the fix are also advised to download another patch to prevent a possible resulting problem in Outlook 2007's Business Contact Manager.

Arnold said Microsoft will monitor the effectiveness of this patch to see what other performance problems to address next, if any.

In the long run, she said the company is "definitely investigating" whether to re-architect Outlook's use of .PST files for local storage, as some users have requested. But she also warned that users shouldn't view their active .PST file as long-term storage for e-mail.

"Outlook wasn't designed to be a file dump, it was meant to be a communications tool," she said. "There is that fine line, but we don't necessarily want to optimize the software for people that store their e-mail in the same .PST file for ten years."