The message does not appear completely but seems to be “550 5.7.1 Client does not have permissions to send as this sender”. Obviously the user does have the permissions (the user was the owner of the mailbox itself).
Thanks to… http://sanjaysingh11.blogspot.com.es/2013/12/550-571-client-does-not-have.html I got this problem solved by configuring this permission:
Run AdsiEdit and select the following path:
Configuration – Services – Microsoft Exchange – <MY_ORG_NAME> – Administrative Groups – Exchange Administrative Group – Servers – <MY_SERVER_NAME> – Protocols – SMTP Receive Connectors:
Properties of the “Client Proxy <MY_SERVER_NAME>” receive connector, “Security” tab and grant the “Accept Authoritative Domain Sender” allow permission for the “Authenticated users”.
Dont forget to grant it for each of your servers.
If you also get errors configuring the IMAP service, check my post:
Exchange 2013 – IMAP NTLM authentication error