Having the same problem. All new mail in the last week and a half show the sender as "CN=username/O=/OU="

I have tried reinstalling both the lotus and outlook clients, wiping out ini file, and changing every preference and setting possible. Then I did a fresh install of all components on another system using only the same id file...and again the problem was there. So I agree it's a domino admin change somewhere.
Any ideas? I can no longer sort or easily find mail with this formatting. I have spent a dozen hours trying to resolve so any help would be appreciated.
Thanks in advance!