If you ever get the following errors

Feb  6 14:31:22 server sendmail[10862]: dangerous permissions=40777 on queue directory /var/spool/clientmqueue/

Feb 6 14:31:41 server sendmail[10875]: NOQUEUE: SYSERR(root): can not chdir(/var/spool/clientmqueue/): Permission denied

This means that the permissions for the folder /var/spool/clientmqueue/ are incorrect

simply correct the error by running the following commands

chown -R root:smmsp /var/spool/clientmqueue

chmod 770 /var/spool/clientmqueue