Microsoft is to hold off the release of a major security update to its Outlook 98 and 2000 email software until next week.

The delay will allow Microsoft to make certain last-minute modifications to the software in response to feedback from customers, the company said in a written statement.

Microsoft originally planned to release the update this week, but the statement issued late yesterday said the software patch will now be available some time next week.

New to the update will be a set of tools that will give administrators more say in what email attachments are allowed through to the user desktop, Microsoft said.

The beta version of the software, which was released last week, included a set of predefined file types -- the ones most likely to contain a virus -- to be automatically removed when received whether containing a virus or not. Users could add file types but not remove any from the master list.

Based on customer feedback, the update will now allow administrators of systems where files are scanned at network level to modify the master list and decide exactly which files users can see.

Microsoft, which stressed security was its number one concern when designing the Outlook patch, said the change does not weaken the security of the systems because additional scanning at network level is also taking place.