cannot read contents of parent directory of ... - check permissions and ownership

Hello everyone

I am trying to setup getmail to retrieve email from Gmail and I am stuck at
the following error messages (on each retrieved email):

Delivery error (maildir delivery 22103 error (127, maildir delivery process
failed (cannot read contents of parent directory of
/mnt/1TB1/backup/gmail/mails/ - check permissions and ownership)))
  msg  1/12 (9033 bytes) from <[email protected]>, delivery error (maildir
delivery 22103 error (127, maildir delivery process failed (cannot read
contents of parent directory of /mnt/1TB1/backup/gmail/mails/ - check
permissions and ownership)))

The structure of the directory is

root@srv /m/1/b/gmail# pwd
/mnt/1TB1/backup/gmail

root@srv /m/1/b/gmail# ls -la
total 32
drwxr-xr-x 4 wojtek root  4096 Oct 12 11:11 ./
drwx------ 4 root   root  4096 Oct 12 11:02 ../
drwxr-xr-x 2 wojtek root  4096 Oct 12 11:21 conf/
-rw-r--r-- 1 wojtek root 14971 Oct 12 11:21 log.txt
drwxr-xr-x 5 wojtek root  4096 Oct 12 11:12 mails/

My configuration file is

root@srv /m/1/b/gmail# cat ./conf/getmailrc
[retriever]
type = SimpleIMAPSSLRetriever
server = imap.gmail.com
username = [email protected]
password = mypassword

[destination]
type = Maildir
path = /mnt/1TB1/backup/gmail/mails/
user = wojtek

[options]
verbose = 2
message_log = /mnt/1TB1/backup/gmail/log.txt
#read_all = false
#delivered_to = false
#received = false

I am not sure how to understand this message, as /mnt/1TB1/backup/gmail/ (which
is the parent of /mnt/1TB1/backup/gmail/mails/) belongs to user wojtek. *Who
(= which user) exactly cannot read which content?*