implement PLT-6469 - Send HELO request containing domain name to SMTP server (#6322)

i18n/en.json

@@ -5902,6 +5902,10 @@
   {
     "id": "utils.mail.connect_smtp.open_tls.app_error",
     "translation": "Failed to open TLS connection"
+  },
+    {
+    "id": "utils.mail.connect_smtp.helo.app_error",
+    "translation": "Failed to set HELO"
   },
   {
     "id": "utils.mail.new_client.auth.app_error",
@@ -5911,6 +5915,10 @@
     "id": "utils.mail.new_client.open.error",
     "translation": "Failed to open a connection to SMTP server %v"
   },
+  {
+    "id": "utils.mail.new_client.helo.error",
+    "translation": "Failed to to set the HELO to SMTP server %v"
+  },
   {
     "id": "utils.mail.send_mail.close.app_error",
     "translation": "Failed to close connection to SMTP server"