Outlook Express's email account settings are stored in the registry. I've never used one of those old INI files myself, but I suspect that just modified the registry directly.
To get a feel for the values that need to be set, use RegEdit and export HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts
Note that if you have multiple OE identities, the info might be in a different place than above, and will probably be at HKEY_CURRENT_USER\Identities
instead.
But, I'm not sure if mucking around in a user's registry is the best way to go about it though, especially since the information could be in completely different parts of the registry if the user has multiple identities. This is probably why you don't see such INI files around anymore.
Might be better to set up a VBA config script or something more interactive.