If you want to pull all clients address, phone numbers, email addresses, etc you can gather this with a backup of your data. Click here for instructions for running a data backup. Once the backup is pulled, open your Client spreadsheet and you will have your list of Client names, address, phone number, email, etc. to save or edit as needed from there.
You can also gather contact emails by running a Client List Report via Reports in your system on the Entry & User tab. After you click Generate for this report you will want to click on Show Advanced Filters and then check the box for "Show contact details", to pull the email data. You can then export this into Excel and manipulate the data as needed.