Ubuntu 16.04 LTS has the latest Evolution 3.18 release. It's generally against Ubuntu's SRU policy to allow new major versions (3.18 > 3.20) into a stable release.
https://wiki.ubuntu.com/StableReleaseUpdates If you need a newer version of Evolution, I encourage you to consider upgrading to Ubuntu 17.10. Ubuntu 17.10 is not a LTS so you will need to upgrade to 18.04 LTS in 6-9 months. But Ubuntu 17.10 does have Evolution 3.26.1. ** Changed in: evolution (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to evolution in Ubuntu. https://bugs.launchpad.net/bugs/1728679 Title: upgrade-software-version for Xenial Status in evolution package in Ubuntu: Invalid Bug description: The version of Evolution in Xenial, 3.18.5.2-0ubuntu3.2, is very old, and has bugs, such as "destination is read only" on a webdav folder. I have been told it was corrected in the later versions, thereefore I would like to request an upgrade of this software for Xenial which you know is a LTS which will be supported until 2021. Thanks for considering this request. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/evolution/+bug/1728679/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp