For JIRA 3.6.2, I tried to follow the intruction to add Custom Field value to email notification: http://confluence.atlassian.com/display/JIRA/Adding+Custom+Fields+to+Email

I found out that $issue.getCustomFieldValue("customfield_10000") does not return anything. Instead, $issue.getCustomField("customfield_10000") returns something. For example, printing out $issue.getCustomField("customfield_10000") or $issue.getCustomField("customfield_10000").name returns the name of the specified custom field. However, the actual cutom field values associated with the issue cannot be retrieved even though clearly, they exist.

I have tried the following commands in the velocity template, but they all fails to return any value:
$issue.getCustomFieldValue( "10000" )
$issue.getCustomFieldValue( "customfield_10000" )
$issue.getCustomField("customfield_10000") -> returns the name of the customer field
$issue.getCustomFieldValue( $issue.getCustomField("customfield_10000") )
$issue.getCustomField("customfield_10000").customFieldValue
$issue.getCustomField("customfield_10000").value
$issue.getCustomField("customfield_10000").value($issue)
$issue.getCustomField("customfield_10000").getValue($issue)
$issue.getCustomField("customfield_10000").getValue($issue).name
$issue.getCustomField("customfield_10000").getValue($issue).value
$issue.getCustomField("customfield_10000").getValueFromIssue($issue)
$issue.getCustomField("customfield_10000").getValueFromParams($params)
$issue.getCustomField("customfield_10000").getCustomFieldValues($params).transformObjectsToStrings()

What is the right command to retrieve the custom field value from velocity template?