Slack for Windows

What's new in this version:

Features:
- Search now supports the NOT operator as long as there is a positive search term. (ex: in:inbox NOT is:unread)

Fixes:
- A major issue has been resolved that prevented IMAP accounts (including Yahoo, Yandex, etc.) from being connected correctly. I'm sorry it's taken so long for this patch to be released. Thanks to @Kozzi11 for the fix and everyone for helping to track down the bug.
- Disabling image autoloading now works consistently and also prevents requests for external stylesheets and web fonts that could be used for tracking
- Mailspring no longer gets "stuck" creating all drafts and replies in plaintext in some cases
- Localizations have been improved for Simplified Chinese and Russian, and @dvomaks added a Ukranian translation! All three have been added to the "verified localizations" list so they're easier to find in the language dropdown.
- If your machine's hostname contains spaces, Mailspring will strip them when identifying itself to SMTP servers to avoid being rejected in some cases. If it cannot determine your hostname it will fall back to your IP address similar to how Thunderbird works.
- Deleting a "Found in Mail" contact from a CardDAV account (Fastmail, etc.) no longer causes sync to crash.
- On Linux, Mailspring now depends on python2 for Ubuntu 20
- On Linux, Mailspring's lists itself as a "Mail Client" rather than saying "Mailspring Mailspring"
- When downloading attachments, Mailspring will not overwrite files in the selected folder and will choose unique names for attachments with the same name
- The LinkedIn URLs in the contact sidebar no longer contain duplicate in/in/ fragments in some cases
- In the composer, lines containing a single space or starting with a single space are now preserved upon sending
- Sent mail reminders look better in the ui-dark theme and returning to the reminders view after clearing the last reminder no longer causes a crash