diff --git a/server/auth/email.js b/server/auth/email.js
index d2b5392d..135bd3d2 100644
--- a/server/auth/email.js
+++ b/server/auth/email.js
@@ -20,7 +20,7 @@ router.post('email', async ctx => {
   ctx.assertEmail(email, 'email is required');
 
   const user = await User.findOne({
-    where: { email },
+    where: { email: email.toLowerCase() },
   });
 
   if (user) {
diff --git a/server/commands/userInviter.js b/server/commands/userInviter.js
index 1bcfeaa9..356b393a 100644
--- a/server/commands/userInviter.js
+++ b/server/commands/userInviter.js
@@ -17,14 +17,22 @@ export default async function userInviter({
 }): Promise<{ sent: Invite[] }> {
   const team = await Team.findByPk(user.teamId);
 
-  // filter out empties, duplicates and obvious non-emails
-  const compactedInvites = uniqBy(
-    invites.filter(invite => !!invite.email.trim() && invite.email.match('@')),
+  // filter out empties and obvious non-emails
+  const compactedInvites = invites.filter(
+    invite => !!invite.email.trim() && invite.email.match('@')
+  );
+
+  // normalize to lowercase and remove duplicates
+  const normalizedInvites = uniqBy(
+    compactedInvites.map(invite => ({
+      ...invite,
+      email: invite.email.toLowerCase(),
+    })),
     'email'
   );
-  const emails = compactedInvites.map(invite => invite.email);
 
-  // filter out existing users
+  // filter out any existing users in the system
+  const emails = normalizedInvites.map(invite => invite.email);
   const existingUsers = await User.findAll({
     where: {
       teamId: user.teamId,
@@ -32,11 +40,11 @@ export default async function userInviter({
     },
   });
   const existingEmails = existingUsers.map(user => user.email);
-  const filteredInvites = compactedInvites.filter(
+  const filteredInvites = normalizedInvites.filter(
     invite => !existingEmails.includes(invite.email)
   );
 
-  // send and record invites
+  // send and record remaining invites
   await Promise.all(
     filteredInvites.map(async invite => {
       const transaction = await sequelize.transaction();
diff --git a/server/commands/userInviter.test.js b/server/commands/userInviter.test.js
index 53c85edc..f75aab71 100644
--- a/server/commands/userInviter.test.js
+++ b/server/commands/userInviter.test.js
@@ -43,7 +43,7 @@ describe('userInviter', async () => {
     const response = await userInviter({
       invites: [
         { email: 'the@same.com', name: 'Test' },
-        { email: 'the@same.com', name: 'Test' },
+        { email: 'the@SAME.COM', name: 'Test' },
       ],
       user,
       ip,