Windows 10 x64
1.4.0-549b7968
--
Bug?
Every time the client syncs new email, regardless of whether or not there is new email a tiny blue badge appears on the tray icon.
I believe this indicator should only appear when there is new unread email since, when you click and open the window, the badge disappears until the next sync.
Badge after mail sync:

Regular state:

No
No
No
me too (blue dot on every sync) and it only works if mailspring is minimized NOT closed to tray, Also the actual blue dot is so small i cant even see it without Kmag.
Manjaro KDE
I've installed Mailspring on Ubuntu 14 and this happens on Linux too. It was driving me mad seeing a blue dot on the notification icon but then (after spending a few minutes hunting around the 4 IMAP accounts that I connect to) came across this thread and it's related bug in Mailspring.
However, I'm hanging in with Mailspring as I think it's the neatest and easiest to use across the board. I do like their (monthly subscription based) option of tracking emails that are sent / opened, although I'm not using it presently.
I think I see the issue: https://github.com/Foundry376/Mailspring/blob/master/app/internal_packages/system-tray/lib/system-tray-icon-store.es6#L54
return isWindowBlurred
? { iconPath: INBOX_UNREAD_ALT_ICON, isTemplateImg: false }
: { iconPath: INBOX_UNREAD_ICON, isTemplateImg: true };
I assume isWindowBlurred is true, and so it always sets the iconPath to be INBOX_UNREAD_ALT_ICON which is set on line 15.
However this goes against what @JackDinn said:
it only works if mailspring is minimized NOT closed to tray
If it's minimized, it will also probably say that the window is blurred.
when i said "it only works if mailspring is minimized NOT closed to tray" i meant that the unread mail icon (blue badge) only works when mailspring is minimized although it has this error of showing with every sync. However the blue unread badge does not show at all if i have mailspring closed to tray.
I have inverse case. Blue bage not shows

Windows 10 x64
Can confirm on Windows 10 x64. I always get a blue dot after a sync, even with 0 unread messages.
Can confirm on Linux Mint 19.1 Cinnamon. Icon keeps turning blue, no new mail.
Same here. Blue dot while there is no new mail.
It could be great to disable this, and have a email counter badge instead.
(Windows 10 x64)

This issue is supposed to be fixed by #1206
Any progress on this? Have been having this issue in Ubuntu 19.10. I think a solution was given in #1206 but hasn't been committed to master.
I have Mailspring 1.7.2 with Ubuntu 18.04. I do not see a blue dot on the tray icon, but the whole tray icon which is white randomly turns into blue.
Mailspring version 1.7.4-d54ff730 on ubuntu 19.10 has the same issue.
Most helpful comment
me too (blue dot on every sync) and it only works if mailspring is minimized NOT closed to tray, Also the actual blue dot is so small i cant even see it without Kmag.
Manjaro KDE