BTW, for the "dot" thing, the mailbox separator in Cloudron is ".". This is why folders with dot don't work. If you create a folder named "foo.bar.baz", it is like subfolder bar under foo and subfolder baz under bar.
While using "." as a seperator is not a bug as such, using "/" as a separator instead of "." would have been a better choice for Cloudron but we didn't know this when we started (sadly, "." is the dovecot default too). And also using "/" as separator is required for mailbox sharing to work. We are slowly working towards moving the separator to be "/", step by step.