I don't see any related issue reported on the GitHub site for MATE Desktop:
I don't know enough about it ... but ... using dconf-editor, and go to
/org/ayatana/indicator/datetime
there are a number of configurable options. Notably:
show-calendar
show-date
show-day
time-format
custom-time-format
My system default format string for this last one, custom-time-format, is
%l:%M %p
giving "8:52 PM".
For something like ... 20:44 _ Fri Aug 15 ... the format string needs to be changed to
%R _ %a %b %d
NOTE: I did all that, but it had no effect, even when I toggled "Use system default" to OFF! Also, modifying the time-format parameter had no impact either.
Don't know if those are supposed to have relevance or not but, given they are specific to ayatana, I expected them to have some! 
What my test instances for the Apps are currently showing:
For the linkage with Evolution, there was a previously reported issue which may be relevant to what you are experiencing.
There is a package,
ayatana-webmail
but I see no equivalent referencing Evolution!
However there is a package,
evolution-plugins
which references e-mail notifications.