diff --git a/lib/bamboo/adapters/rfc2822_with_bcc.ex b/lib/bamboo/adapters/rfc2822_with_bcc.ex
index 7bd770c..84872fb 100644
--- a/lib/bamboo/adapters/rfc2822_with_bcc.ex
+++ b/lib/bamboo/adapters/rfc2822_with_bcc.ex
@@ -200,30 +200,75 @@ defmodule Bamboo.SesAdapter.RFC2822Renderer do
       |> Integer.to_string()
       |> String.pad_leading(2, "0")
 
+  # this function has been duplicated while from a PR in progress in `DockYard/elixir-mail`
+  defp put_parts(message, parts) do
+    put_in(message.parts, message.parts ++ parts)
+  end
+
+  # this function has been duplicated while from a PR in progress in `DockYard/elixir-mail`
+  defp delete_all_parts(message) do
+    put_in(message.parts, [])
+  end
+
+  # this function has been duplicated while from a PR in progress in `DockYard/elixir-mail`
+  defp is_inline_attachment?(message),
+    do: Enum.member?(List.wrap(Mail.Message.get_header(message, :content_disposition)), "inline")
+
+  defp split_attachment_parts(message) do
+    Enum.reduce(message.parts, [[], [], []], fn part, [texts, mixed, inlines] ->
+      cond do
+        match_content_type?(part, ~r/text\/(plain|html)/) ->
+          [[part | texts], mixed, inlines]
+        is_inline_attachment?(part) ->
+          [texts, mixed, [part | inlines]]
+        true -> # a mixed part - most likely an attachment
+          [texts, [part | mixed], inlines]
+      end
+    end)
+    |> Enum.map(&Enum.reverse/1) # retain ordering
+  end
+
   defp reorganize(%Mail.Message{multipart: true} = message) do
     content_type = Mail.Message.get_content_type(message)
 
-    if Mail.Message.has_attachment?(message) do
-      text_parts =
-        Enum.filter(message.parts, &match_content_type?(&1, ~r/text\/(plain|html)/))
-        |> Enum.sort(&(&1 > &2))
+    [text_parts, mixed, inlines] = split_attachment_parts(message)
+    has_inline = Enum.any?(inlines)
+    has_mixed_parts = Enum.any?(mixed)
+    has_text_parts = Enum.any?(text_parts)
 
+    if has_inline || has_mixed_parts do
+      # If any attaching, change content type to mixed
       content_type = List.replace_at(content_type, 0, "multipart/mixed")
       message = Mail.Message.put_content_type(message, content_type)
 
-      if Enum.any?(text_parts) do
-        message = Enum.reduce(text_parts, message, &Mail.Message.delete_part(&2, &1))
-
-        mixed_part =
+      if has_text_parts do
+        # If any text with attachments, wrap in new part
+        body_part =
           Mail.build_multipart()
           |> Mail.Message.put_content_type("multipart/alternative")
+          |> put_parts(text_parts)
 
-        mixed_part = Enum.reduce(text_parts, mixed_part, &Mail.Message.put_part(&2, &1))
-        put_in(message.parts, List.insert_at(message.parts, 0, mixed_part))
+        # If any inline attachments, wrap together with text
+        # in a "multipart/related" part
+        body_part = if has_inline do
+          Mail.build_multipart()
+          |> Mail.Message.put_content_type("multipart/related")
+          |> Mail.Message.put_part(body_part)
+          |> put_parts(inlines)
+        else
+          body_part
+        end
+
+        message
+        |> delete_all_parts()
+        |> Mail.Message.put_part(body_part)
+        |> put_parts(mixed)
       else
+        # If not text sections, leave all parts as is
         message
       end
     else
+      # If only text, change content type to alternative
       content_type = List.replace_at(content_type, 0, "multipart/alternative")
       Mail.Message.put_content_type(message, content_type)
     end
diff --git a/lib/bamboo/adapters/ses_adapter.ex b/lib/bamboo/adapters/ses_adapter.ex
index fd4ecbb..45719f4 100644
--- a/lib/bamboo/adapters/ses_adapter.ex
+++ b/lib/bamboo/adapters/ses_adapter.ex
@@ -71,12 +71,10 @@ defmodule Bamboo.SesAdapter do
       attachments,
       message,
       fn attachment, message ->
-        headers =
-          if attachment.content_id do
-            [content_id: attachment.content_id]
-          else
-            []
-          end
+        headers = Map.get(attachment, :headers) || []
+        headers = if attachment.content_id,
+          do: [{:content_id, attachment.content_id} | headers],
+          else: headers
 
         opts = [headers: headers]