Unique email addresses

Hi -

I can't find any documentation on this question.  If we send out an email to a custom group which contains multiple records with the same email address, will Netsuite deliver our campaign to that email address multiple times (ie once for each record), or is it smart enough to only send emails once to each unique address?

As a follow-up, is there any way to create a custom search which only pulls up records with a unique value on a specific field?

The reason why I ask is that we'd like to do a campaign to our existing customers, but for each customer we often have multiple jobs, which may or may not have different email addresses associated with them.  We'd like to include the job records as part of the search group for the email blast, but don't want to risk sending out multiple emails to a single address for our more frequent customers.