Added flowmailer recognition

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -1803,6 +1803,12 @@ public class MessageHelper {
                 return "zoho";
         }
 
+        String return_path = imessage.getHeader("Return-Path", null);
+        if (!TextUtils.isEmpty(return_path)) {
+            if (return_path.contains("flowmailer.com"))
+                return "flowmailer";
+        }
+
         return null;
     }
 

app/src/main/res/values/strings.xml

@@ -1815,6 +1815,7 @@
 
     <string name="infra_awsses" translatable="false">Amazon SES</string>
     <string name="infra_elastic" translatable="false">Elastic Email</string>
+    <string name="infra_flowmailer" translatable="false">Flowmailer</string>
     <string name="infra_gmail" translatable="false">Gmail/Gsuite</string>
     <string name="infra_icloud" translatable="false">Apple/iCloud</string>
     <string name="infra_icontact" translatable="false">iContact</string>