A new Microsoft Outlook Express feature to help users send large e-mail attachments has backfired and could be used to crash mail servers, according to BugNet.
Outlook Express users can get around file size limitations many Internet service providers (ISPs) put on their e-mail systems by breaking large files into many small documents. The problem is that user can elect to make the fragments as small as 16Kb, which means that a single large file can be transformed into thousands of separate e-mail messages, all targeting a single electronic in-box.
Al Reust, an owner of Seattle-area ISP, TSCNet, found the problem, which he says can make "mail bombs" that can overload servers by sending them more mail than they can handle.
"The latest version of Netscape Communicator is some 19.8MB large. If I attach that to an e-mail, and Outlook Express is set to break them into 16Kb, well, divide 20MB by 16Kb -- you get tens of thousands of e-mails, all pointing at my server."
BugNet reports that an independent ISP confirmed the problem exists, and can even sneak through most firewalls.
"It's a neat feature," Reust says. "But the 16Kb block is just not big enough."
"Microsoft plans to implement some kind of dialog box that will prompt the user to set the chunk size to a higher level than 16K," said Harry Goodwin, product manager at Microsoft. "We hate to get rid of this feature, since it's something we've been asked to provide."