As everyone else has said, yes, you have to turn off passcode to jailbreak.
Also, as an IT manager, when you add your corporate work email to your phone, you loose some ownership of the phone and the content that's work related, if somehow they find out your device is jailbroken, and its against any policy they have, you might find your IT department may remotely wipe your phone (I'm sure there's a tweak to prevent that out there somewhere) and/or reprimand you (again based on company policies).
Also, as an IT manager, I find satisfaction in remotely wiping employees' devices because they failed to abide by company policies regarding devices and mobile email (my company owns the phone), so, just proceed with caution if you are jailbreaking a company owned phone.