In recent months, when Hacker News users have asked for suggestions, I've recommended them. However, I cannot in good faith do that at this time, because I've discovered a flaw that could be quite problematic. For me, it's mostly just really annoying.
The issue was discovered because Outlook for Android does not give you options for which folders you see when connected via IMAP. So after I had inadvertently created an Archive folder, and subsequently deleted it, it continued to show up in Outlook, and I could not (and still cannot) find a way to hide it.
What I discovered via the WebMail that NameCheap Private Email provides is that they do not delete folders, ever. Worse, the emails inside of "deleted" folders are also not deleted. For the sake of convenience, I took 4 screenshots, and uploaded them to imgur: https://imgur.com/a/4RdzQjY
1. A folder with an email in it is deleted
2. I empty the trash
3. Going over to settings > mail > change imap subscriptions, I can see any deleted folders still exist and are merely unsubscribed by NameCheap Private Email's webmail client. I re-subscribe and save.
4. The folder is back, along with the email inside.
I've reached out to support, but so far have only been able to reach a level of support that attempts to walk me through how to use their webmail, including deleted folders and emptying the trash. I'm hoping I can escalate it further so that an issue can be opened and resolved.
One more note - while I demonstrated above using their webmail, the same happens if I use Thunderbird, and delete folders. They are not deleted, but merely hidden from some clients. However, other clients, like Outlook for Android, continue to see these hidden folders.