Outlook does not cause SPAM. Spam comes to your email address no matter what you use to view it!
Hullo! - Good morning!
I realize that, however the bulk emailers utilize services that scan servers gleaning the addresses- including group addresses- to include on the mailing list. We get spam coming in to Army addresses that are for internal and official use only, and some that mimics a 'group' as the sender that is sent to the members of the group. It is hacking. Some clients, such as Outlook, have address books that are more susceptible to it than others. We got some spam with Notes, but there were mechanisms that could be implemented that made dealing with it manageable. Outlook is a headache- the only argument for it is the way it works serverside. I would never choose it for my own personal client.