Well, a bit of background to start with, in near past we had Evolution mail integrating quite well with Linux DE's (if not very well with Gnome exclusively), we could just close the client but keep on receving alerts about mails coming in etc.
now, evolution mail is something of the past and Geary doesn't even meet most of the requirements, it is (for me) evolution shrinked down and made non-functional at all; now there is thunderbird, nice client that does good job and getting modernized in a col way but still the DE's integration is missing, as far as I know Thunderbird is widely adopted by Linux communities and Lovers, more than windows or anything else, there should be at least a level of integration into DE's like firefox do offer, an extension that makes the client integrate and even when closed, users can still receive alerts about their mails; Zach from the Solus team just let me knew about an external plugin to do that, which is nice but I (like many other) cares about safety when it comes to mails or browsing and do prefer if the client itself was capable of that, like natively.
Possible to integrate such functionality?
Would help and make people smile for sure.