Everyone should feel comfortable to bring their whole self to work, not be fearful, not to hide.
Understanding and respecting that gender is not always binary, and respecting people's identity by addressing them in an appropriate way is one step we can take towards creating more inclusive and open workplaces. This awareness and respect in turn creates a more inclusive and open world.
At the most basic level, we should never start with an assumption of gender. When addressing emails to an unknown recipient or mailbox, prefer something like "To whom it may concern," or "Dear Readify Careers mailbox," over a presumptive "Dear sir,".
Building on that, when addressing someone we know, we should also respect their gender identity by using the pronouns that align to the gender they identify with. There are a number of different ways people who don't identify with a specific gender may like to be referred to, but to keep things simple, pronouns might look a bit like this:
I identify as male, and my gender pronouns are "he", "him" and "his".
I make this information available in my email signature so that people know how I should be addressed:
I've personally almost never had a problem with being addressed improperly, but I know it happens all the time with my female colleagues (emails titled assuming male recipient), and it must be very frustrating for people whose gender identity is non-binary or non-conforming. This is a small step towards encouraging others to be considerate about how they refer to people, and the impact it can have.