THINK YOU HAVE problems with your e-mail system? Be thankful you\u2019re not running IT at AOL Time Warner. Many Time Warner employees are incensed over the recent announcement that America Online will become the primary corporate e-mail system for the merged media conglomerate, whether employees like it or not.AOL is not the first technology company to insist that its employees use its own product. Microsoft employees are discouraged from using Apple\u2019s Mac, and Sun Microsystems employees are not supposed to use Microsoft products. But Time Warner workers say the AOL system is slow, hard to navigate and doesn\u2019t provide business features that publishing professionals depend on. For instance, one IT professional notes that AOL is less efficient than some rival systems in attaching files to messages and in including the original message in a reply. Another, who also wished to remain anonymous, says the system lacks a way to set up an automatic response to incoming messages. "AOL is great to use at home, but in the workplace, it just won\u2019t cut it," says one employee of a Time Inc. magazine. "I can\u2019t imagine how many times during the day I\u2019d hear \u2019You\u2019ve got mail.\u2019" AOL users can shut off the disembodied voice but cannot dismantle the feature. At Time Inc., where employees have used Lotus\u2019s cc:Mail product since 1995, CIO Paul Zazzera declined to discuss details of the switch. But he did note that the change will most likely require an added level of security. Rather than logging on to the network by typing in a name and password, he says, employees will need to type in a number that appears on a digital card. Because the number changes every few seconds, however, employees in the know allege that the device will create headaches whenever they log on.While few insiders say they think the transition will be smooth, some benefits should emerge before long. Ann Brackbill, an AOL Time Warner spokeswoman, says employees will be able to access AOL\u2019s e-mail system from "just about anywhere," and will be able to use AOL\u2019s instant messaging system to communicate with colleagues, instead of sending dozens of e-mails back and forth. The new system should be up and running by fourth quarter, pumping more money into AOL\u2019s coffers.