Extracting an an integer value from an xml column
You should use the value() method of the XML data type.

If your XML structure looks like this:

&lt;DLR&gt;
  &lt;siteID&gt;12345&lt;/siteID&gt;
&lt;/DLR&gt;


Your query would be

select msg.value('(/DLR/siteID/text())[1]', 'int') as DOMAIN
from dbo.YourTable


But it does however not look like you have an XML column at all since msg like '&lt;DLR%' is invalid against XML columns.

Then you need to either modify your table so the column is XML or you can cast to XML in your query.

select cast(msg as xml).value('(/DLR/siteID/text())[1]', 'int') as DOMAIN
from dbo.YourTable