Great article Max, thank you. As David points out there are larger compliance considerations and we thank you for also pointing out your archiving partners who can assist in this space. Sidbar; there is an email forensics team internal to Microsoft somewhere and this group's opinion would be interesting.
Onto a question I have - ArchiveSink is particular to Exchange Servers in that it relies on Event Sink stuff from Exchange. Is there a way (and I haven't done any R&D, this just popped up at the right time) where an IIS SMTP Server can be made to drop a copy of all messages passing through to a disk queue for "archiving"? EML format would be suitable. Or perhaps another way of doing essentially what ArchiveSink does, but without Exchange involved? I'm thinking of SMTP gateway boxes where IIS alone is being used.
Cheers