Problem

After migration to a new Exchange 2007/2010 server, MailGate started bouncing messages back to senders with the following error:

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“530 5.7.1 Client was not authenticated": This is the Axway MailGate program at host xxxx.

I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can delete your own text from the attached returned message.

The Axway MailGate x.x.x program

host 1.1.1.1 [1.1.1.1] said: 530 5.7.1 Client was not authenticated (in reply to MAIL FROM command)
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If Transport Layer Security (TLS) is enabled on Exchange server(s), then anonymous login needs to be enabled as well.

To allow an anonymous application (i.e. MailGate) to relay off of Exchange 2007/2010 server(s), follow the steps below:

1. Create a new Receive Connector for MailGate: Server Configuration -> Hub Transport -> Receive Connectors.
2. Add the MailGate's IP Address
3. Once the new custom Receive Connector is created, go into the properties of this connector, go to the Permission Groups Tab > Add Anonymous Users

In the Authentication Tab, only Transport Layer Security will be selected. This is called Opportunistic TLS which means that TLS will be accepted and is the preferred method for communication, but TLS will not be required.