PROBLEM
You are unable to relay with an SMTP error 5.7.57 Client was not authenticated.
You have configured an anonymous relay connector on your Exchange server and entered the source IP address of the sending system. However the client is redirected to the default connector which tries to authenticate the sender and throws error 5.7.57 Client was not authenticated.
CAUSE
This can happen if you have multiple IP addresses on the sending host and it is sending from an address other than the one you entered in the relay connector configuration.
SOLUTION
There is a fairly easy way to determine the sending IP address:
- From the sending system open the Telnet client and try to connect to your Exchange server on port 25.
- Type ehlo.
- The Exchange server will greet you, mentioning the IP address the connection is originating from.
CEO at Exchangemaster GmbH
Dejan Foro is founder and CEO of Exchangemaster GmbH.
He lives in Zurich, Switzerland and is a dedicated specialist, with 30 years of professional work experience in IT.
Before starting Exchangemaster GmbH he worked as a system engineer and project manager with customers of all sizes and across many industries: From small ISV startups and a NGO humanitarian organizations up to largest international corporations like Stryker, Swisscom, British Telecom and Nyrstar.
He spent his entire career delivering Microsoft based infrastructure solutions with main focus on Active Directory and Exchange. During those years, he collected a valuable work experience on 8 Exchange generations (2019, 2016, 2013, 2010, 2007, 2003, 2000 and 5.5) and has delivered services to a user base of more than 3.2 million mailboxes in on-premise, hybrid and Office 365 deployments.
Beside working on customer projects, he is a regular speaker and expert at Microsoft conferences and user groups. As a Microsoft Certified Trainer he also teaches Microsoft Official Curriculum courses to technical professionals around Europe.
For his work he has received numerous awards.
In 2005 he was the first member to be elected into the MCP Hall of Fame by Windows IT Pro Magazine readers choice (as 1 of 6 worldwide).
From 2005-2017, Dejan has been awarded by Microsoft Corporation with the yearly Microsoft Most Valuable Professional award in area of Exchange for 12 years in a row (one of approximately 100 worldwide and, at the time, the only 1 such in Switzerland).
He lives in Zurich, Switzerland and is a dedicated specialist, with 30 years of professional work experience in IT.
Before starting Exchangemaster GmbH he worked as a system engineer and project manager with customers of all sizes and across many industries: From small ISV startups and a NGO humanitarian organizations up to largest international corporations like Stryker, Swisscom, British Telecom and Nyrstar.
He spent his entire career delivering Microsoft based infrastructure solutions with main focus on Active Directory and Exchange. During those years, he collected a valuable work experience on 8 Exchange generations (2019, 2016, 2013, 2010, 2007, 2003, 2000 and 5.5) and has delivered services to a user base of more than 3.2 million mailboxes in on-premise, hybrid and Office 365 deployments.
Beside working on customer projects, he is a regular speaker and expert at Microsoft conferences and user groups. As a Microsoft Certified Trainer he also teaches Microsoft Official Curriculum courses to technical professionals around Europe.
For his work he has received numerous awards.
In 2005 he was the first member to be elected into the MCP Hall of Fame by Windows IT Pro Magazine readers choice (as 1 of 6 worldwide).
From 2005-2017, Dejan has been awarded by Microsoft Corporation with the yearly Microsoft Most Valuable Professional award in area of Exchange for 12 years in a row (one of approximately 100 worldwide and, at the time, the only 1 such in Switzerland).
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