From 7ac7fe2cfecbbd93e1150df10fb4cee69c11d6db Mon Sep 17 00:00:00 2001
From: Mike Perry <mikeperry@torproject.org>
Date: Mon, 26 May 2014 14:56:28 -0700
Subject: [PATCH] Issue 3559: Use From or ReplyTo hostname in Message-ID if
 available.

I wrote this fix to avoid obviously specifying that I am using a mobile device
to reply to an email.

Others want this for ease of filtering messages from their host by Message-ID.
---
 src/com/fsck/k9/mail/internet/MimeMessage.java | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/com/fsck/k9/mail/internet/MimeMessage.java b/src/com/fsck/k9/mail/internet/MimeMessage.java
index d80b7bb22..c37abe02d 100644
--- a/src/com/fsck/k9/mail/internet/MimeMessage.java
+++ b/src/com/fsck/k9/mail/internet/MimeMessage.java
@@ -313,7 +313,22 @@ public class MimeMessage extends Message {
     }
 
     private String generateMessageId() {
-        return "<" + UUID.randomUUID().toString() + "@email.android.com>";
+        String hostname = null;
+        if (mFrom != null) {
+            int hostIdx = mFrom[0].getAddress().lastIndexOf("@");
+            hostname = mFrom[0].getAddress().substring(hostIdx);
+        }
+
+        if (hostname == null && mReplyTo != null) {
+            int hostIdx = mReplyTo[0].getAddress().lastIndexOf("@");
+            hostname = mReplyTo[0].getAddress().substring(hostIdx);
+        }
+
+        if (hostname != null) {
+            return "<" + UUID.randomUUID().toString() + hostname + ">";
+        } else {
+            return "<" + UUID.randomUUID().toString() + "@email.android.com>";
+        }
     }
 
     public void setMessageId(String messageId) throws UnavailableStorageException {