I think it is time to consider a jump in the Postfix major version
number, so that the next stable release will be Postfix 3.0 and not
2.12.
1) There are changes in the Postfix build system that are visible
only to people who build Postfix from source (mainly distribution
maintainers and some hard-core Postfix users). These changes were
needed to support Postfix shared libraries and dynamic loading of
Postfix database plugins.
2) There is a change that is visible to anyone who manages a Postfix
mail system: better default settings with support for backwards
compatibility (BC). The BC support could be streamlined further,
but it will always require an explicit action to turn off BC and
to make some, all, or no, "old" behavior permanent in main.cf or
master.cf.
3) There are many smaller changes: SMTPUTF8; different settings for
different Milters or policy services; lookup tables such as pipemap,
randmap, unionmap, and more to come; replacing a Postfix delivery
agent's delivery status and/or descriptive text; main.cf expansion
of ${logical-expr?if-true:if-false}, and logical expressions with
relational operators for numbers and strings.
Based on the changes in 1) and 3) alone I was already considering
a jump in the major version number. This would have been similar
to Linux where the change in major number happened without major
visible changes in functionality.
However with the incompatible changes in 2), I think that a major
version number change is necessary. This may cause some delays in
adoption, but I think it is only fair to people who have come to
expect that upgrading Postfix is a no-brainer, because due to the
changes in 2), I think is is not a no-brainer.
Wietse
