Honestly, IT should just really ask "What do you want your email address to be?" and not auto-assign. Just give IT a general alias so that your chat name, email address, source control account, or any other account, can all be the same. The issue is that some people are going to want the same exact alias and then that creates a back and forth but at bigger places, IT should be able to cut out some time to make a system to check if a username is taken and just send that to new hires. For smaller places, collisions like that are less likely to happen.