Exchange- RecipNotFound


  • Hi,


    Exchange and anti spam(proofpoint) in DMZ.

    If I send e-mail to non-existent e-mail address in my organization

    I receive error

    #550 5.1.1 RESOLVER.ADR.RecipNotFound; not found ##

    But if I send e-mail to non-existing e-mail address outside of my organization e.g. Gmail

    I dont receive any error in outlook.

    Proofpoint logs has error user unknow

    but sender doesnt receive any information in outlook.

    Where should I start  troubleshooting ?Exchange or anti spam?
    Friday, April 20, 2018 1:36 PM

All replies

  • Perhaps GMail isn't issuing an NDR to the invalid recipient.  Perhaps Proofpoint is blocking the NDR.

    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!

    Saturday, April 21, 2018 12:39 AM
  • If I send mail from proton mail
    to non existing Gmail address  I receive NDR


    : host[] said: 550-5.1.1 The email account that you tried to reach does not exist. Please try 550-5.1.1 double-checking the recipient's email address for typos or 550-5.1.1 unnecessary spaces. Learn more at 550 5.1.1 s10-v6si4979026wrs.10 - gsmtp (in reply to RCPT TO command)

    It must be Exchange or proofpoint

    Monday, April 23, 2018 5:14 AM
  • Hi,

    if user is not listed in Proofpoint, then it will generate and NDR and send it to recipient (you might have this disabled, so check it). 

    Please check the following:

    In Proofpoint, check to see if user exist. If user is not searchable in Proofpoint, you need to sync that user from local AD or create account manually in Proofpoint. Proofpoint uses a per user license model. No license = no email.

    Does email arrive successfully if sent by internal user?

    Please mark as helpful if you find my contribution useful or as an answer if it does answer your question. That will encourage me - and others - to take time out to help you. Thank you! Off2work

    Monday, April 23, 2018 5:39 AM