Please note: These are general points, which apply to *any* application that uses a MySQL database. They are not particular to simpleContact.
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MySQL database connection
In the majority of cases, your MySQL database server is accessible through the default setting of "localhost". However some hosts choose to store their databases elsewhere.
On DreamHost, every database has a unique host name, which you specify when you create the database.
You can set this information under Goodies / MySQL in your control panel.
Reference: Creating a MySQL Database (DreamHost support wiki)