diff --git a/core/server/services/mega/mega.js b/core/server/services/mega/mega.js
index 9c64d86ba8..bd261ad06d 100644
--- a/core/server/services/mega/mega.js
+++ b/core/server/services/mega/mega.js
@@ -26,9 +26,9 @@ const getEmailData = async (postModel, members = []) => {
     members.forEach((member) => {
         emails.push(member.email);
 
-        // firstname is a computed property only used here for now
+        // first_name is a computed property only used here for now
         // TODO: move into model computed property or output serializer?
-        member.firstname = (member.name || '').split(' ')[0];
+        member.first_name = (member.name || '').split(' ')[0];
 
         // add static data to mailgun template variables
         const data = {
diff --git a/core/server/services/mega/post-email-serializer.js b/core/server/services/mega/post-email-serializer.js
index 7d8b492928..ec48902452 100644
--- a/core/server/services/mega/post-email-serializer.js
+++ b/core/server/services/mega/post-email-serializer.js
@@ -60,7 +60,7 @@ const _parseReplacements = (emailTmpl) => {
     const EMAIL_REPLACEMENT_REGEX = /%%(\{.*?\})%%/g;
     // the " is necessary here because `juice` will convert "->" for email compatibility
     const REPLACEMENT_STRING_REGEX = /\{(?<memberProp>\w*?)(?:,? *(?:"|&quot;)(?<fallback>.*?)(?:"|&quot;))?\}/;
-    const ALLOWED_REPLACEMENTS = ['subscriber_firstname'];
+    const ALLOWED_REPLACEMENTS = ['first_name'];
 
     const replacements = [];
     ['html', 'plaintext'].forEach((format) => {
@@ -77,7 +77,7 @@ const _parseReplacements = (emailTmpl) => {
                         format,
                         id,
                         match: replacementMatch,
-                        memberProp: memberProp.replace('subscriber_', ''),
+                        memberProp,
                         fallback
                     });
 
diff --git a/test/api-acceptance/admin/email_preview_spec.js b/test/api-acceptance/admin/email_preview_spec.js
index ac473c713e..1e1d77a0a7 100644
--- a/test/api-acceptance/admin/email_preview_spec.js
+++ b/test/api-acceptance/admin/email_preview_spec.js
@@ -75,7 +75,7 @@ describe('Email Preview API', function () {
                 id: ObjectId.generate(),
                 title: 'Post with email-only card',
                 slug: 'email-only-card',
-                mobiledoc: '{"version":"0.3.1","atoms":[],"cards":[["email",{"html":"<p>Hey {subscriber_firstname \\"there\\"} {unknown}</p><p><strong>Welcome to your first Ghost email!</strong></p>"}],["email",{"html":"<p>Another email card with a similar replacement, {subscriber_firstname, \\"see?\\"}</p>"}]],"markups":[],"sections":[[10,0],[1,"p",[[0,[],0,"This is the actual post content..."]]],[10,1],[1,"p",[]]]}',
+                mobiledoc: '{"version":"0.3.1","atoms":[],"cards":[["email",{"html":"<p>Hey {first_name \\"there\\"} {unknown}</p><p><strong>Welcome to your first Ghost email!</strong></p>"}],["email",{"html":"<p>Another email card with a similar replacement, {first_name, \\"see?\\"}</p>"}]],"markups":[],"sections":[[10,0],[1,"p",[[0,[],0,"This is the actual post content..."]]],[10,1],[1,"p",[]]]}',
                 html: '<p>This is the actual post content...</p>',
                 plaintext: 'This is the actual post content...',
                 status: 'draft',