This is my
<urlrewrite>
<rule>
<name>Canonical Hostnames</name>
<condition name="host" operator="equal">^example\.com</condition>
<condition name="host" operator="notequal">^$</condition>
<from>^/(.*)</from>
<to type="redirect" last="true">http://www.example.com/$1</to>
</rule>
</urlrewrite>
It is redirectiing well to www.example.com but the problem is http://example.com/resetpassword/?user=2560256&token=1233 is redirected to http://example.com/resetpassword
To preserve the query string, you can add the use-query-string parameter to the urlrewrite element as follows:
<urlrewrite use-query-string="true">
Alternatively, you can include the query string in your redirect URL as follows:
<to type="redirect" last="true">http://www.example.com/$1?%{query-string}</to>
See the documentation here.