diff --git a/src/route/hkp.js b/src/route/hkp.js
index 4fed747..be26616 100644
--- a/src/route/hkp.js
+++ b/src/route/hkp.js
@@ -43,7 +43,7 @@ class HKP {
       ctx.throw(400, 'Invalid request!');
     }
     const origin = util.origin(ctx);
-    await this._publicKey.put({emails: [], publicKeyArmored, origin});
+    await this._publicKey.put({publicKeyArmored, origin});
     ctx.body = 'Upload successful. Check your inbox to verify your email address.';
     ctx.status = 201;
   }
diff --git a/src/route/rest.js b/src/route/rest.js
index 89b6307..3d95a25 100644
--- a/src/route/rest.js
+++ b/src/route/rest.js
@@ -43,7 +43,7 @@ class REST {
       ctx.throw(400, 'Invalid request!');
     }
     const origin = util.origin(ctx);
-    await this._publicKey.put({emails: emails ? emails : [], publicKeyArmored, origin});
+    await this._publicKey.put({emails, publicKeyArmored, origin});
     ctx.body = 'Upload successful. Check your inbox to verify your email address.';
     ctx.status = 201;
   }
diff --git a/src/service/pgp.js b/src/service/pgp.js
index ef40005..3613a1a 100644
--- a/src/service/pgp.js
+++ b/src/service/pgp.js
@@ -136,7 +136,7 @@ class PGP {
           result.push({
             status: userStatus,
             name: uid.name,
-            email: uid.address.toLowerCase(),
+            email: util.normalizeEmail(uid.address),
             verified: false
           });
         }
@@ -154,7 +154,7 @@ class PGP {
   async filterKeyByUserIds(userIds, armored) {
     const emails = userIds.map(({email}) => email);
     const {keys: [key]} = await openpgp.key.readArmored(armored);
-    key.users = key.users.filter(({userId: {email}}) => emails.includes(email));
+    key.users = key.users.filter(({userId: {email}}) => emails.includes(util.normalizeEmail(email)));
     return key.armor();
   }
 
@@ -187,7 +187,7 @@ class PGP {
    */
   async removeUserId(email, publicKeyArmored) {
     const {keys: [key]} = await openpgp.key.readArmored(publicKeyArmored);
-    key.users = key.users.filter(({userId}) => userId.email !== email);
+    key.users = key.users.filter(({userId}) => util.normalizeEmail(userId.email) !== email);
     return key.armor();
   }
 }
diff --git a/src/service/public-key.js b/src/service/public-key.js
index 21ac05f..5cc3878 100644
--- a/src/service/public-key.js
+++ b/src/service/public-key.js
@@ -68,7 +68,8 @@ class PublicKey {
    * @param {Object} origin             Required for links to the keyserver e.g. { protocol:'https', host:'openpgpkeys@example.com' }
    * @return {Promise}
    */
-  async put({emails, publicKeyArmored, origin}) {
+  async put({emails = [], publicKeyArmored, origin}) {
+    emails = emails.map(util.normalizeEmail);
     // lazily purge old/unverified keys on every key upload
     await this._purgeOldUnverified();
     // parse key block
@@ -267,7 +268,7 @@ class PublicKey {
       queries = queries.concat(userIds.map(uid => ({
         userIds: {
           $elemMatch: {
-            'email': uid.email.toLowerCase(),
+            'email': util.normalizeEmail(uid.email),
             'verified': true
           }
         }
@@ -332,6 +333,7 @@ class PublicKey {
    * @return {Array}          A list of user ids with nonces
    */
   async _flagForRemove(keyId, email) {
+    email = util.normalizeEmail(email);
     const query = email ? {'userIds.email': email} : {keyId};
     const key = await this._mongo.get(query, DB_TYPE);
     if (!key) {
diff --git a/src/service/util.js b/src/service/util.js
index 816cb85..2c24c24 100644
--- a/src/service/util.js
+++ b/src/service/util.js
@@ -78,6 +78,18 @@ exports.isEmail = function(data) {
   return re.test(data);
 };
 
+/**
+ * Normalize email address to lowercase.
+ * @param  {string} email   The email address
+ * @return {string}       lowercase email address
+ */
+exports.normalizeEmail = function(email) {
+  if (email) {
+    email = email.toLowerCase();
+  }
+  return email;
+};
+
 /**
  * Create an error with a custom status attribute e.g. for http codes.
  * @param  {number} status    The error's http status code