Fixes issue #2894 - Emails with binary body (attachment as body) get handled as if they were text messages which breaks the attachment.

app/models/channel/email_parser.rb

@@ -574,13 +574,27 @@ process unprocessable_mails (tmp/unprocessable_mail/*.eml) again
   def collect_attachments(mail)
     attachments = []
 
-    # Add non-plaintext body as an attachment
-    if mail.html_part&.body.present? ||
-       (!mail.multipart? && mail.mime_type.present? && mail.mime_type != 'text/plain')
+    attachments.push(*get_nonplaintext_body_as_attachment(mail))
+
+    mail.parts.each do |part|
+      attachments.push(*gracefully_get_attachments(part, attachments, mail))
+    end
+
+    attachments
+  end
+
+  def get_nonplaintext_body_as_attachment(mail)
+    if !(mail.html_part&.body.present? || (!mail.multipart? && mail.mime_type.present? && mail.mime_type != 'text/plain'))
+      return
+    end
+
     message = mail.html_part || mail
 
-      filename = message.filename.presence ||
-                 (message.mime_type.eql?('text/html') ? 'message.html' : '-no name-')
+    if !mail.mime_type.starts_with?('text/') && mail.html_part.blank?
+      return gracefully_get_attachments(message, [], mail)
+    end
+
+    filename = message.filename.presence || (message.mime_type.eql?('text/html') ? 'message.html' : '-no name-')
 
     headers_store = {
       'content-alternative' => true,
@@ -589,23 +603,19 @@ process unprocessable_mails (tmp/unprocessable_mail/*.eml) again
       'Charset'             => message.charset,
     }.reject { |_, v| v.blank? }
 
-      attachments.push({ data:        body_text(message),
+    [{
+      data:        body_text(message),
       filename:    filename,
-                         preferences: headers_store })
+      preferences: headers_store
+    }]
   end
 
-    mail.parts.each do |part|
-
-      new_attachments = get_attachments(part, attachments, mail).flatten.compact
-      attachments.push(*new_attachments)
+  def gracefully_get_attachments(part, attachments, mail)
+    get_attachments(part, attachments, mail).flatten.compact
   rescue => e # Protect process to work with spam emails (see test/fixtures/mail15.box)
     raise e if (fail_count ||= 0).positive?
 
     (fail_count += 1) && retry
-
-    end
-
-    attachments
   end
 
   def get_attachments(file, attachments, mail)