I guess I can see where there may be some possible security ramifications of not exposing whom has such large attachments but I'd also like the ability, as an administrator, if I need to start restricting the size of attachments who am I most likely to start affecting.  And other legitimate administrator concerns.  Perhaps "leaning" on some people as to whether or not they need such stuff.

You can go the opposite way. This need some handwork and provides only a snapshot, but it works.

• Create a batchfile with one entry for every DAOS enabled database:

"C:\Program Files\IBM\Domino\nserver.exe" -c "tell daosmgr listnlo -o output_mailfile1.txt ALL mail/mailfile1.nsf"
"C:\Program Files\IBM\Domino\nserver.exe" -c "tell daosmgr listnlo -o output_mailfile2.txt ALL mail/mailfile2.nsf"

• Run batch
• Do a text search for the required nlo file over all the created output_*.txt files