First consult the Evolution Manual.
The evolution-list mailing list is the best place to seek further assistance with using Evolution, for example when you have problems.
The evolution-hackers mailing list is for discussions among developers. The topics can get pretty technical.
Many Evolution developers and users can also be found on IRC (irc.gimp.org), channel #evolution.
Bugs and feature requests can be filled under GNOME issue tracker, depending on the place of the issue, but it's fine when it's filled against other project, because issues can be moved between projects there. Evolution still use the old GNOME bugzilla for the old reports, but any new issues should be filled in the current issue tracker, namely for evolution-data-server, evolution, evolution-ews and evolution-mapi. Always search it for any existing reports, even closed, to not create unnecessary duplicates. Also mention your versions, because it's possible that the issues had been already fixed (especially when Long Term Support distributions provide older versions).
Evolution in Flatpak
Flathub contains the latest stable version. Users can build and run the latest stable (or development) Evolution in Flatpak, even on older distributions. A detailed guide can be found on the Evolution Flatpak sub-page.
Get the Source Code
The Evolution project releases its source code as tarball files, from which Free Software distributors can create easily-installable binary packages for users.
Most likely your Free Software distribution (Fedora, Mint, Ubuntu, etc.) already provides binary packages for Evolution. The following links are only for the source code.
The latest stable releases are the 3.38 series. Tarballs can be found for these various components (see also the ".news" files accompanying them for a list of changes):
evolution-ews 3.38.x (optional, for Microsoft Exchange servers)
evolution-mapi 3.38.x (optional, for old Microsoft Exchange servers)
The latest development snapshot tarballs (3.39 series, what will become 3.40) can be found below (after the first 3.39 release):
evolution-ews 3.39.x (optional, for Microsoft Exchange servers)
evolution-mapi 3.39.x (optional, for old Microsoft Exchange servers)
Or you can clone the source code repositories with git:
git clone https://gitlab.gnome.org/GNOME/evolution-data-server.git (Browse)
git clone https://gitlab.gnome.org/GNOME/evolution.git (Browse)
git clone https://gitlab.gnome.org/GNOME/evolution-ews.git (optional, for Microsoft Exchange servers) (Browse)
git clone https://gitlab.gnome.org/GNOME/evolution-mapi.git (optional, for old Microsoft Exchange servers) (Browse)
You can also view the schedule of upcoming releases.
How to Build Evolution from sources
Camel (for email)
The following materials have aged. Some parts are no longer accurate and need a rewrite.
Evolution-EWS (Exchange Web Services)
Exchange Web Services operations feature's parity matrix with /EWS (evolution-ews)
IRC nick names in brackets.