Mac Messenger 3.5.4 was available to download from 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. The application lies within Communication Tools, more precisely Texting & Video calls. The actual developer of this free software for Mac is Jef Geskens & Vidal van Bergen.
From the developer:
Mac Messenger is a client for the MSN instant messaging protocol. You can use it to chat with your friends who have MSN Messenger. Mac Messenger is intended to be fast, stable, and easy to use. It features full contact management, single and group chat, emoticons, fonts and colors.
You may want to check out more Mac applications, such as Go for Messenger: Voice & Text Message Chat, Interaction Messenger or Enterprise Messenger, which might be similar to Mac Messenger.