Why isn't Postfix updated?

Question

postfix

Hello.
It costs Ubuntu server 14.04. I install Postfix from a repository, I check the version.

[email protected]:~$ postconf -d | grep mail_version
mail_version = 2.11.0

The version is not bearded, but not the newest. The latest one is already 3.#.# ( cdn.postfix.johnriley.me/mirrors/postfix-release/i... )
Am I doing something wrong or is this an Ubuntu problem?
Thank you.