This site facilitates a simple way to group email all members of LWW. To send a group email, use your normal email application and address it to landingsww@celeris.com. All members will receive the email.
You can respond to group emails in two ways, the whole group or to the sender. To respond to the group do a Reply List (may be Reply All on your app). To respond to the sender, just to Reply.
Does the new website have a list of members and phone numbers?