If you are looking to make the settings on all new entries then I believe that Paul’s answer will fix your problem. However, if you are looking to make batch updates there are other issues. The new Admin client allows for a lot more control on the ACl without having to visit each database in the system. However, it does not get all the way.
Our Workflo!ACL Manager allows you to or delete any person/group or Role from any selected databases including the other ACL settings like Delete Documents etc. The updates are then run either immediatly or via a scheduled agent after hours (Large updates can be pretty time consuming, like add an Admin group to every mail DB). In addition you can create queries to determine what rights a person/group/role has on a specific DB, or selected DBs or all DBs. Great for auditing the security of your system. You can download a free demo that will process the first 30 databases that it finds from our site at http://www.wfs.com IMHO it is a pretty good deal at $250.00
It states in the admin help that if you import the text file in to the user registration you can change the mail file owner acecss setting to all the new users
For setting the entries for a database you do so by adding the entry in the template surrounded by that way every databases created from that template will have those settings already set.
But you can;t use this meathod for the mail user because it obviously changes for each user.