Downloading MailContacts 3.0 for Mac from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this app available. The software lies within Communication Tools, more precisely E-mail. The actual developer of this Mac application is treeinspired GmbH. We recommend checking the downloaded files with any free antivirus.
From the developer:
MailContacts scans through your e-mails and presents you with all the contacts you interacted with. In addition, the application allows you to add the addresses missing within your address list with just a click. It even summarizes similar addresses and differentiates between unknown contacts and the ones that are already in your address book.
You may want to check out more software for Mac, such as Address Book to HTML, YAI or Encrypt Mail, which might be similar to MailContacts.