Most legislative offices have adequate staff resources to respond only to their constituents.
The inclusion of your full name and mailing address will allow your legislator to determine if your residence is within his or her legislative district. Naturally, when sending email to members of a committee, send individual email to them and indicate that, as a Washington State citizen, you wish to communicate with them. In this case, put the mailing address at the end of the message, as they may otherwise trash it. Ten contacts from ten different people are much more effective than one contact from ten people - consider sending ten separate messages with slightly different wording. Personalizing gets better responses - if you have met the official or know personal details about them, add it to the text.