Nine Digit Zip Code Question

[AaronHebert1]

I am trying to find out if there is a good way to find nine digit zip codes. I work for a non-profit Soil and Water Conservation District and we would like to send out a mailer. To get the bulk mailing price we are required to use a nine digit zip code we only have a five digit code. It seems there are a lot of companies that are selling this data. The lowest price I have seen is about 300 dollars. We have about 400,000 records that need the nine digit zip code. Is there any way I can use the Address Locator to populate the nine digit zip code?

[KyleDixon]

To look up ZIP4s individually: https://tools.usps.com/go/ZipLookupAction!input.action

Also, if you're doing a bulk mailing, take a look at this: USPS.com® - Every Door Direct Mail‌

It's a mapping tool that lets you geographically select an area to send mail by carrier route, it's the equivalent of handing a carrier a stack of letters and asking him to stick one in every mailbox on his route.