I see no need to change the version number for mostly
backward-compatible changes, given that:
You must work for the MS library guys who gave us two DLL's of the same
version that were "Mostly compatible" but broke almost any app that wasn't
designed directly for that version.
This was known for years as DLL HELL !
Don't do it.
It's a simple software rule.
NEW VERSION = NEW VERSION NUMBER
Users will have to update their spf records, its fact of life. That's the
whole point of version numbers.
Richard.