Updating /etc/mail/access file the milter processes can generate “open error hash … Permission denied” errors.
When the files are automatically updated the permissions on the .db files will be changed back to only allow root to read them, if you are OK with anyone with an account on the box reading the files you can resolve this issue as follows:
Edit the /etc/mail/Makefile and find the section
%.db: % @makemap hash $@ < $<
Add a new line after this and put in the following text
@chmod a+r $@
Ensuring you use a TAB in the Makefile
Now everytime the file is updated the permissions on the db file will be set to allow all users on the box to read the files which includes the milter processes.