In one client which I have data from so far the reduction in disk space from doing the following was 13% on average per user with a high of 37%.
Note some users already used some of these settings, imagine if your network never used ANY of them!
load compact -c from the console to move all your files to ODS 51(on whole server or just mail directory up to you)
DAOS (but this only went into effect today, but should be interesting 30 days out)
Compress Document Data
Compress Database Design
Plus a few more could be done but we don't want to use them right now.
Want to do it in one quick process?
1) See my previous post on DAOS enablement and the DCT tuner. DCT can provide some more pros/cons to some other benefits in this area.
2) open your 8.5 lotus Admin client
3) Go to the Files Tab then your mail directory
4) CTRL-A to select all
5) Select Advanced properties from the Database tools on your Right column.
6) check off the ones to use
And don't forget to run compact -c and CREATE_R85_DATABASES=1 in your notes.ini so all future files get it too!