Unusable

I've tried everything recommended on the support pages, including a full, clean uninstall and reinstall. I've been in contact with the support team for a couple of weeks with the final outcome being "Yep, this is an issue and we've added it to the backlog" and then with today's update, Spark Mail became totally unusable.

Starting about a month ago, Spark Desktop (on Windows) would no longer open or download attachments. It also required me to re-authorize Outlook mail accounts on a daily basis. This is all survivable, but frustrating because it no longer served well as a unified inbox.

Then with today's update, Spark became totally unusable. Not only has the software stopped responding to any inputs, but it continues to open and close itself until I manage to kill all of the processes for it in Task Manager. I can't just kill the open instance in Task Manager, because when I do, it begins to re-open itself. I have to kill the open instance, then find the new instance down in the background process list and kill that too, or it will open and close itself into eternity.

So, forgive the bad form with this question, but are there any other good options that can give me a unified inbox on Windows for 6 email accounts without an absurd subscription fee? (I really hate Outlook's app, so I'm hoping that's not the only option.)