Mailbox almost full but isn't true

[mrmarkuz (Markus Neuberger)]

I suspect it’s a Thunderbird issue. Did you already try to reconfigure Thunderbird?

Maybe related:

New mail quota ignored after limit has been exceeded

Please have a look at /var/log/maillog, and see if you can find any relevant log message. Then find the maildirsize file of your user and paste here its contents find /var/lib/nethserver/vmail/ -name maildirsize ... cat /var/lib/nethserver/vmail/USERNAME/Maildir/maildirsize Just to have an idea of mailbox disk size (should not be exactly the same of mail quota) du -h -s /var/lib/nethserver/vmail/USERNAME