I've been a Notes/Domino person for as long as I can remember and in all that time, I've never seen a virus acting within the mail client.

Funnily enough, although I almost never use outlook, I've seen virus activity in the mail client far more times that I can count.

Is outlook less secure than Notes? Probably. Is it less common and therefore has less viruses associated with it. Again, Probably.

Personally though, I think it comes down to differences in the degree and type of automation that the developers (Microsoft and IBM) permit in terms of external automation.

Since most of the time, the additional "hooks" in outlook are a liability, not a benefit, surely Microsoft could offer ways to turn them off?