[mtmail]

https://semver.org/ describes it best

    Given a version number MAJOR.MINOR.PATCH, increment the:

    MAJOR version when you make incompatible API changes,
    MINOR version when you add functionality in a backwards compatible manner, and
    PATCH version when you make backwards compatible bug fixes.

Ideally you'd only have to worr about major version change, while all others should be backward compatible.