My self and and many other have had problem with the one-TAB format. It
would be interesting to learn if there are any particular reson for this
There isn't. The format is designed to be machine-parseable with ease, and
machine-generatable. It is meant to be used in conjunction with custom,
site-specific management tools.
As a reference example, consider webadmin. It provides the ability to
create most common smtpaccess entries, from a simple web-based form. After
webadmin updates the smtpaccess file, makesmtpaccess is invoked
Manual editing of smtpaccess is not required. You should not need to edit
smtpaccess directly, unless you're doing diagnostics or debugging. As such,
the question is moot.