Our eblasts just recently started going to the Junk folders for every member in our organization (Outlook users), and I suspect they are also going to our member-clients' Junk/Spam folders, too. Did something change on Emma's end for the filters to change, or how do I tackle this ?
I'm sorry to hear you're seeing high amounts of filtering! This can be due to several factors including the Outlook user's domain settings, the content (down to the words used) of the emails, and even how your settings are setup.
You could start by reviewing content in your email and see if its dramatically different from past emails, then perhaps see if there are trends in the domains when looking at who's inboxes filtered to spam and who's didn't.
Lastly, a large email size can sometimes be automatically filtered by most inboxes (Outlook can be stricter than others.). Consider this when including images / styling in your mailing.
I hope this helps point you in the right direction! Let me know if I can clarify any of the above!