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OnPrem Exchange 2010 Server rejects all messages from one Office365 pure cloud sender RRS feed

  • Question

  • I reaching out i the hope someone came across this issue or could shed some light.

    We are using an OnPrem Exchange 2010 SP3 in a hybrid setup.

    The issue suddenly occurred. All messages from one cloud user to internal or external recipients are rejected. The sample mail flow is like when I send from o365 to Internet, it should first go to the on-prem, then on-prem send it to internet.   But the messages seems to be rejected from the on-prem everytime. Actually we don't want to re-configure the hybrid wizard because other users have no issue. Only this specific user has this issue. I have also tested on the OWA from other machine and it can be reproduced.  It seems that on-prem server only rejects that sender.


    Here is the error

    #550 5.7.10 The e-mail account does not exist at the organization this message was sent to. Check the e-mail address before re-sending. ##

    Here is the connection encryption message

    Message sent to webmail.mydoimain.com at <myIP> using TLS1.0 with AES256

    Monday, July 15, 2019 7:22 AM

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