Despite what many people say, usage of you guys as non-gendered address, similar to the regional y'all, is rather well-established: https://english.stackexchange.com/questions/11816/is-guy-gen.... However, in corporate environments it's still a good maxim to be mindful of people who have non-standard sensibilities, e.g. I personally use you guys as email address only for all-male group of recipients.