@AZorin . Yes be good for us to know if parts of Evolution are critical to ZorinOS.
Any ideas about where Thunderbird icon(s) should be located for them to work as shortcuts etc?
There are so many items of malware that can be introduced via email, so have to be wary all the time, particularly in Windows environment.
usr | share | applications | Thunderbird 
You can copy and paste to your desktop (well I can in Cinnamon DE which is what I have just done to check - not sure about Gnome.
Yes, the evolution-data-server is used by the Online Accounts feature which is a part of the desktop. Despite sharing a name with the Evolution app, it acts more like a library and can function independently of the mail/groupware app.
It's not recommended to remove the evolution-data-server packages from the system in order to keep this functionality and maintain system stability, as it's a dependency of the desktop.
@AZorin . Thanks for your answer, much appreciated. I am just glad that I sought advice before removing those two âEvolutionâ items and so avoided a breakage.
@swarfendor437
Well that location has the generic mail client icon showing against Thunderbird, so explains why that is on my desktop and not the bird.
The proper icons at:
/usr/lib/thunderbird/chrome/icons/default
are just different size .png image files of the bird.
I give up. I thought it was going to be easy to swap the icon, but seems not the case.
On my build, the thunderbird icon used is whichever icon set I am using. I am using Zorin-ish⊠So, it should really be the same thunderbird as you.
IF that is the case, then it should be easy to provide an icon for Thunderbird- As I make Icon Sets all the time, I do it with each set I make.
Mine has always been the default icon - apart from where somehow I appear to have two of them (have I been hacked?) in the menu, plus I have two waterfox icons - very strange stuff!
@swarfendor437. Are you are talking about duplicates at usr/share/applications ? If so, you are not alone. A small number of applications are listed twice and smaller number 3 times. I donât know if that is a bad thing or not.
@Aravisian. I am not overly concerned that I do not have the normal blue bird icon for my Thunderbird menu or desktop shortcuts. I thought it may be possible to simply pick an alternative icon from a list, but seems not the case. It is not worth expending more effort to fix, especially as may be corrected if I have to reinstall Thunderbird for Z16 
More:
Aravisian got me thinking about themes. I use simple Zorin95 icons. However, if I switch to Gnome (or anything other than Zorin95) then I get the blue bird icon for Thunderbird. So the problem here seems to be associated with Zorin95 icons. I will not change to one of the other icon sets just for a blue bird, but strange that the Zorin95 set is only one that is different.
Thatâs because Zorin-95 uses âpaperâ (flat) icons. I alway prefer hicolor - which is probably why I get the mythological Thunderbird icon.
An icon theme can include an "inherit" list. This list accounts for icons that may be missing in the set by allowing the system to fallback to a different set to 'inherit' the missing icons from that set, rather than leave a black imageless gap.