Members are required to add their email address (so you can authenticate your account when you first join, and to receive notifications from NetGalley) and country of residence (for territory rights purposes when publishers receive your requests). You may opt to make your email address not visible to publishers.
Members are not required to include their full mailing address or phone number, but have the ability to do so. If you choose to include this information, you have the option to make it not visible to publishers. If you do make it visible to publishers, then only publishers who you have accessed titles from can view it.
To make any contact information (email address, mailing address, phone number) invisible to publishers, just click the "eye" icon and once there is a slash through it, your information will stay hidden. See below for an example where you will see the email address is visible but the Address and Phone are not visible to publishers.