I do not have much experience with using Domino language packs. As I have to work with them in a project next week I just did some tests. To have it handy in future I document here how upgrading to Notes 8 mail file design in a specific language works:
First, install the desired language packs on top of your Domino server
Then you have to submit the following commands on the Domino server console:
To upgrade e.g. all mail files in the mail directory to R8 in German language independent from the current mail file design you have to use the following commands:
| load convert -gGerman -u mail/ * mail8.ntf | |
| load compact mail/ |
The compact command releases the space the design elements in the original language had used.
In the same way you can change the language of a mail file later, e.g. to change one specific file to English you use the commands:
| load convert -gEnglish -u mail/demo.nsf * mail8.ntf | |
| load compact mail/demo.nsf |