EXCHANGE   Exchange – SMTP error: 550 5.7.1 Client does not have permissions to send as this sender



Problem

Last week I was testing the IMAP/SMTP connection of my Exchange 2013. Unexpectedly Outlook returned the following error:
Exchange - SMTP error 550 5.7.1 Client does not have permissions to send as this sender

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).

Resolution

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