7 Replies Latest reply on Apr 12, 2018 11:37 PM by Sanford Whiteman

    Email auto reply Issue

    Vipula Dhamija


      Yesterday we launched an email around 2 pm PST to a very small segment of lead DB.

      Around 8:00 pm PST we received around 200 auto-replies in outlook inbox. I tried to search for the domain or email in my DB but I could not find anything related to the email below in my DB. All the auto-replies has the same domain- ".itscom.net'.


      Below are the details of errors-

      Original Message Details

      Created Date:

      4/12/2018 3:01:29 AM

      Sender Address:


      Recipient Address:



      1. ITSCOM.NET: Email Confirmation

      Error Details

      Reported error:

      550 5.0.350 Remote server returned an error -> 550 #5.1.0 Address rejected.

      DSN generated by:


      Remote server:



      Is this Marketo delivery issue or some Microsoft outlook issue. I searched the web but could not find any resolution to that. I am not a domain or email deliverability expert so looking for suggestions to resolve the issue.




        • Re: Email auto reply Issue
          Sanford Whiteman

          While this could be due to buggy filtering at O365 -- see this thread from today -- you need to be precise about the domain(s) that's generating the error.


          s00.itscom.net isn't the same as itscom.net. They have different MX records and so should be considered completely separate, as if they were apples.com and oranges.com.


          In your database, is the recipient @itscom.net or @ the subdomain? Is it possible that you did a bulk load of people at a certain subdomain, and they recently discontinued use of that domain, merging the mailboxes into the parent domain? (This can happen when people upgrade their systems to support more users on the same server.)