Download of PostCheck 2.4 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available.
Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe. This Mac application is a product of Brian Toth. The software lies within Internet & Network Tools, more precisely Browser extensions.
From the developer:
PostCheck is a plugin for Apple's Address Book that provides an efficient, one-click way to lookup missing ZIP+4 Codes, Cities and States and will format addresses to meet USPS standards. Also provides Group Lookups.
You may want to check out more software for Mac, such as Arch, Opera Update Checker or AmazonSearch, which might be related to PostCheck.