The 1.6.3 version of GyazMail for Mac was available to download on the developer's website when we last checked. We cannot confirm if there is a free download of this app available.
According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. GyazMail for Mac lies within Communication Tools, more precisely E-mail. This Mac application is a product of jp.gyazsquare.
From the developer:
GyazMail is an e-mail client that is developed from scratch to be a simple, easy-to-use e-mail client with many features, based on the Cocoa framework. This software will be distributed as shareware (undecided on details at this point).
You may want to check out more Mac applications, such as Email Backup Pro, which might be related to GyazMail.