All 4.3 clients can still work with previous 4.x servers except when they expect the server to do name resolution for them, which is only available on 4.3 servers. Please see below for the procedure for building and testing.
New applications can use the frozen configuration while existing ones can use the old configuration.
The use of domain names in configuration files can greatly simplify their setup. Be sure to read the man page on sockd.conf very carefully and consider how well you maaintain your DNS data if you want to use domain names in your configuration files. Chee-Wai Yeung I am almost certain though that I lost a batch of mail messages when I changed my job. In most cases, you should have no needs to modify the Makefiles in the subdirectories. It's a good idea to direct stdout and stderr to a file so that you can see what's being done afterwards.