There is no built-in tool provided on that purpose. If someone scripted that for himself, I cannot say.
It is not that long to do by hand, and it’s more reliable.
Keep a backup of you Names
Create the Mail-in documents one by one, it will takes 2 min per doc : the full name of the mail-in db shall be the same than the fullname of the user (with OU and Org).
Delete all users accounts : either by SUPPR+F9 (if you want to leave them in the Groups), either by standard user removal BUT having unchecked mailbox deletion.
You may check that the Owner of each mail database is still the same as the fullname given in the mail-in doc
I discovered awhile back that the Person and MIDB documents have two fields that dictate whether the document is one (Person) or the other (MIDB). I’m an Admin, not a Programmer, so I created two Simple Agents that change the values of those two fields. Their names: Convert MIDB doc to Person doc and Convert Person doc to MIDB doc. In the People or MIDB view I select the document(s) I want to change and, in the Actions menu, I select the agent to run it. The document disappears from the view (say, People) and appears in the other (say, MIDB) view.
The two field names are Form and Type. The values for a Person document are “Person” and for an MIDB document are “Database”. So, just change the values of those two fields and, voila, you have converted your Person to an MIDB or your MIDB to a Person.
These two are the “obvious” ones for switching between user and MIDB. As the “functional” fields are working the same in both types this is working. It just has some minor disadvantages:
For MIDBs the field “ShortName” is not shown. But if it was filled in person document before switching it is still there and will “work” as an alias. So you might have mails delivered to a mailin-database that you do not expect them to arrive there unless you inspect the document properties
MIDBs also do not have a “Certificate” and “HTTPPassword” field. But still the information is there and might possibly cause some “invisible” problems.
There is no “mail system” field in MIDB. Converting a user with mailsystem = “Other internet mail” (value 5) will result in a database that seemingly works but will forward all mails to the person in “MailAddress” field that is also hidden from view in MIDB-Form
These are just the ones that instantly come to mind, there might be more with other fields.
As you all know: In Notes/Domino in most cases fields will be effective even when hidden or not even shown in a form. And this can of course cause confusion.