Mail first-time impressions, various observations

[tiltX]

I've set up Elementary 8.1 for a novice to medium level computer user and I wanted to share some first-time impressions or issues we had when using the Mail app. I'm happy to send individual bug reports if that is helpful (I know Linux but not enough about elementary OS to know where log files or syslog entries might be found retroactively).

1. On start-up the IMAP account's existing folders were there but they were all empty. I see that this is already covered here: Unable to connect email account after brand new install of Elementary OS 7 #947 (reply in thread) but this is quite a shocker when setting up a new PC ("all my mail is gone!").
2. On another occasion, I started the mail app and the window was completely blank, not even the 3 columns (folders, messages, content) showed up - just the icons in the title bar. There was no way to reload so I quit Mail and restarted it via the dock. Still empty. On the third try, everything was back to normal. There were a bunch of new mails in the inbox. Maybe Mail was refreshing/downloading messages in the background or the network connection was slow? If that was the cause it would be great to show the GUI first or have some kind of progress bar/spinner about what's going on.
3. An e-mail with 6MB of photo attachments (but no other text) sent from an iPhone showed up blank. Maybe this has to do with the way Apple does attachments or something is taking too long to load or decode? This seems like something I could send a bug report for if I knew how and where to submit a test e-mail in a somewhat anonymous way.
4. Clicking on a link in an e-mail didn't open the web browser (the default one... Epiphany?). The browser's icon popped up briefly on the right side of the dock (I think this is an indicator of a background process) but it disappeared again without a browser window opening. When Epiphany is already open clicking on links works perfectly fine.
5. There doesn't seem to be an address book of existing contacts. This is is probably one of the tiny but annoying things of moving the user to Elementary OS: on their previous PC they could just auto-complete any recipient but on Elementary they are starting from a blank slate. They have to type e-mail addresses of all their friends and relatives manually. After an e-mail is sent, the Mail app remembers it. It's not enough to just type an e-mail draft though. You have to send messages akin to "Hi, new PC, just sending out a test" to make Mail learn to auto-complete. There doesn't seem to be a contacts list or address book app. Maybe the Mail app - when an account is used for the first time - could learn former recipients from the account's "sent" folder? Is there a file somewhere that I can pre-fill with e-mail addresses for that user?
6. The user I set the PC up for was used to dragging and dropping e-mails to other folders. This doesn't seem to be supported but there's a "move conversation" button which does the trick.
7. I had set up filters for the user in their previous mail client to move incoming e-mails to specific subfolders (family, shopping, ...). It seems the Mail app doesn't support this. (Which is fine! It's a basic e-mail client. I'd just like to report first impressions).

All together, congrats to making such an elegant Linux desktop! Like I said, I'm happy to collect some logs or submit individual bug reports if appropriate (I have looked through the discussions and issues on github a bit but didn't want to spam the issues list without proper logs or test cases).