I just did a fresh install of roundcube 1.3.10 under Debian 10.1 using nginx, PHP 7.3.4. From the installer I could send a test email and imap login worked fine. I did a first login using my IMAP credentials and it worked fine. RC fetches all folders from my dovecot, but it doesn't fetch any mail. I checked using $config['imap_debug'] = true;, and I could verify that no mail is ever attempted to be fetched. Of course there are mails - I see them in Thunderbird, Nextcloud, Horde, ...
Trying to log out failed due to CSRF. Well, it requires human interaction ... I could not yet figure out which, and according to what I found on the web it seems stange that this error pops up at logout.
As it seems the issue is different from another recent post even if the view is probably similar. But I did not have any issues in the installer.
Thanks for your help,
- lars.