[exim] New install EXIM + Dovecot - auth permission error

Hi folks.

I'm setting up Dovecot and local user accounts on an existing Centos 7 +
EXIM install.

I've added authentication for the local users as:

dovecot_login:
  driver = dovecot
  public_name = LOGIN
  server_socket = /var/run/dovecot/auth-client
  server_set_id = $auth1

dovecot_plain:
  driver = dovecot
  public_name = PLAIN
  server_socket = /var/run/dovecot/auth-client
  server_set_id = $auth1

However, when I try authenticate as a user, the following errors get logged:

2023-02-01 12:50:11 dovecot_login authenticator failed for hub.********
([10.1.1.103]) [**.**.**.**]: 435 Unable to authenticate at present:
unable to connect to UNIX socket (/var/run/dovecot/auth-client):
Permission denied

The socket exists, but does not have suitable permissions.

[root@vps2 exim]# ll /var/run/dovecot/auth-client
srw-------. 1 dovecot root 0 Feb  1 11:47 /var/run/dovecot/auth-client
[root@vps2 exim]#

Is it simply a case of changing ownership / permissions, and if so, what
do I change them to?

If not, can anyone tell me what I need to do please.

Cheers

Gary