Do not display 'Reply-To' if it is identical to 'From'

+++ b/inmail.module
@@ -430,14 +430,20 @@ function inmail_preprocess_inmail_message(&$variables) {
+      if (isset($from) && ($address['address'] == $from['address'])) {
+        continue;

If it is multiple, we should always list them all. We only want to have it removed if it is single and identical to from.

Changed logic to show the reply-to if there are multiple addresses.

Need work since we have the Rfc2822Address now.

+++ b/inmail.module
@@ -430,19 +430,32 @@ function inmail_preprocess_inmail_message(&$variables) {
+    if (count($reply_to) > 1) {
...
+      if (isset($from) && ($reply_to[0]['address'] !== $from['address'])) {

I would prefer to always do the foreach loop and later do the check:
if (count($reply_to)==1 && $reply_to[0]['address'] == $from['address'])..

And then unset the element.

Implement comm #6.

1. +++ b/inmail.module
   @@ -430,14 +430,20 @@ function inmail_preprocess_inmail_message(&$variables) {
   +  $from = $message->getFrom();
   +  if ($from) {
   +    $variables['address_from'] = [
   +      '#type' => 'inmail_message_address',
   +      '#address' => $from,
   +    ];
   +  }
   

   I think we will always have "From" header in a message. Otherwise, the email message is invalid.

2. +++ b/inmail.module
   @@ -430,14 +430,20 @@ function inmail_preprocess_inmail_message(&$variables) {
        foreach ($reply_to as $key => $address) {
   

   $key seems not needed.

3. +++ b/inmail.module
   @@ -430,14 +430,20 @@ function inmail_preprocess_inmail_message(&$variables) {
   +      if (count($reply_to) == 1 && $address->getAddress() === $from->getAddress()) {
   +        return;
   +      }
   

   We should not use early return here. That means, no other preprocess code will be executed. Let's add a test to assert it.

   Also, we should compare email addresses rather than objects. That prevents the case of different names but same email addresses.

4. +++ b/inmail.module
   index ea771b7..49e2971 100644
   --- a/src/Tests/InmailIntegrationTest.php
   
   --- a/src/Tests/InmailIntegrationTest.php
   +++ b/src/Tests/InmailIntegrationTest.php
   

   IMO, we should put these tests in the related mail element test - InmailMessageWebTest.

5. +++ b/src/Tests/InmailIntegrationTest.php
   index 0000000..6350cb9
   --- /dev/null
   
   --- /dev/null
   +++ b/tests/modules/inmail_test/eml/plain-text-reply-to-multiple.eml
   
   +++ b/tests/modules/inmail_test/eml/plain-text-reply-to-multiple.eml
   index 0000000..3481ea7
   --- /dev/null
   
   --- /dev/null
   +++ b/tests/modules/inmail_test/eml/plain-text-reply-to-same-as-from.eml
   

   We have /addresses folder now. What about moving the emails in there?

6. +++ b/tests/modules/inmail_test/eml/plain-text-reply-to-multiple.eml
   @@ -0,0 +1,15 @@
   +Received: from yahoo.mail.com; Fri, 21 Oct 2016 15:38:40 +0200 (CEST)
   
   +++ b/tests/modules/inmail_test/eml/plain-text-reply-to-same-as-from.eml
   @@ -0,0 +1,15 @@
   +Received: from yahoo.mail.com; Fri, 21 Oct 2016 15:38:40 +0200 (CEST)
   

   example.com

7. +++ b/tests/modules/inmail_test/eml/plain-text-reply-to-multiple.eml
   @@ -0,0 +1,15 @@
   +Hi Alice!
   +
   +Congratulation on your passionate work and contribution to poetry.
   +Your works inspires many many people wide world.
   +
   +Sincerely,
   +Bob aka still Bob
   
   +++ b/tests/modules/inmail_test/eml/plain-text-reply-to-same-as-from.eml
   @@ -0,0 +1,15 @@
   +Hi Alice!
   +
   +Congratulation on your passionate work and contribution to poetry.
   +Your works inspires many many people wide world.
   +
   +Sincerely,
   +Bob aka still Bob
   

   Optional: it would be nice to have self-explanatory mail body, mentioning that it contains multiple reply-to addresses etc...

+++ b/inmail.module
@@ -430,14 +430,20 @@ function inmail_preprocess_inmail_message(&$variables) {
+      if (count($reply_to) == 1 && $address->getAddress() === $from->getAddress()) {

Unrelated: $address->getAddress() is pretty confusing.
As a followup we could think about renaming Drupal\inmail\MIME\Rfc2822Address::getAddress() to getEmail() as it's always an email and more intuitive IMHO.

Implemented comm #8. I added in preprocess function break instead of return, break will only finish foreach.
Created follow-up for renaming getAddress().

Committed with comment refinements and now additionally preserving all keys in the preprocess.