Hi,
- Never seen such error! I suppose it’s from the mailserver container? I’ll fire a new test instance and try to get some clue…
- In my experience, doesn’t matter much of the time. I suggest trying first without any (double)quote. Once done, check your instance with https://www.hardenize.com, look at “Email” part in the results.
- About Gallery: please read at bottom of Recommended Update Policy - #8 by smu44. About Office-like apps: Adding Nextcloud Office or Collabora Online to self hosting.