diff --git a/src/com/fsck/k9/mail/Address.java b/src/com/fsck/k9/mail/Address.java
index b49f425c0..a8ef1ee0c 100644
--- a/src/com/fsck/k9/mail/Address.java
+++ b/src/com/fsck/k9/mail/Address.java
@@ -93,6 +93,16 @@ public class Address {
         return mAddress;
     }
 
+    public String getHostname() {
+        int hostIdx = mAddress.lastIndexOf("@");
+
+        if (hostIdx == -1) {
+            return null;
+        }
+
+        return mAddress.substring(hostIdx+1);
+    }
+
     public void setAddress(String address) {
         this.mAddress = address;
     }
diff --git a/src/com/fsck/k9/mail/internet/MimeMessage.java b/src/com/fsck/k9/mail/internet/MimeMessage.java
index 7c6fe6b2c..2f69cba39 100644
--- a/src/com/fsck/k9/mail/internet/MimeMessage.java
+++ b/src/com/fsck/k9/mail/internet/MimeMessage.java
@@ -321,21 +321,21 @@ public class MimeMessage extends Message {
 
     private String generateMessageId() {
         String hostname = null;
-        if (mFrom != null) {
-            int hostIdx = mFrom[0].getAddress().lastIndexOf("@");
-            hostname = mFrom[0].getAddress().substring(hostIdx);
+
+        if (mFrom != null && mFrom.length >= 1) {
+            hostname = mFrom[0].getHostname();
         }
 
-        if (hostname == null && mReplyTo != null) {
-            int hostIdx = mReplyTo[0].getAddress().lastIndexOf("@");
-            hostname = mReplyTo[0].getAddress().substring(hostIdx);
+        if (hostname == null && mReplyTo != null && mReplyTo.length >= 1) {
+            hostname = mReplyTo[0].getHostname();
         }
 
-        if (hostname != null) {
-            return "<" + UUID.randomUUID().toString() + hostname + ">";
-        } else {
-            return "<" + UUID.randomUUID().toString() + "@email.android.com>";
+        if (hostname == null) {
+            hostname = "email.android.com";
         }
+
+        /* We use upper case here to match Apple Mail Message-ID format (for privacy) */
+        return "<" + UUID.randomUUID().toString().toUpperCase(Locale.US) + "@" + hostname + ">";
     }
 
     public void setMessageId(String messageId) throws UnavailableStorageException {
diff --git a/src/com/fsck/k9/preferences/Settings.java b/src/com/fsck/k9/preferences/Settings.java
index 11ecc921a..b4dd8ef41 100644
--- a/src/com/fsck/k9/preferences/Settings.java
+++ b/src/com/fsck/k9/preferences/Settings.java
@@ -35,7 +35,7 @@ public class Settings {
      *
      * @see SettingsExporter
      */
-    public static final int VERSION = 31;
+    public static final int VERSION = 32;
 
     public static Map<String, Object> validate(int version, Map<String,
             TreeMap<Integer, SettingsDescription>> settings,