The problem was something left over from the conversion from 6.5 to 7.03 .
The admin at the time had set up a program on the server:
See NAB (name and address book) names.nsf on the server -> Configuration -> Servers-> Programs
Program name: convert
Command line: -u mail\*.nsf * dwa7.ntf
Server to run on: sa1
Run at times: 18:00 each day
Repeat interval of: 0 minutes
Day of week: Fri
Naughty admin. This should have beeen disabled after the successful conversion to the dwa7 mail templates.
I disabled the program, it was actually on both servers as there was some mail boxes only on the extranet server.