Today we had an issue with one of our Amazon hosted servers. This server was hosting a local SMTP Server (IIS), and was sending out mail on behalf of a domain (let’s say domain: abracadabra.com).

The mail was dropped into the IIS bad mail directory, because our server was prohibited from relaying mail by spamhaus.org.
As we were relaying for abracadabra.com, and our mail server was not known as a mail server from this domain we we’re blocked.

We solved it by sending our mail through the mail server which was responsible for the abracadabra.com by using SMTP Authentication.

• Open the [Properties] of your Default SMTP Server
• Click on the [Outbound Security] button

  

  Fill in your user name and password you use for your remote SMTP Server of the abracadabra domain and click [OK]

• Then click the [Advanced] button and fill in your remote SMTP server in the “Smart host” field.

   

  Click [OK] twice