Hmmm... so it turns out that when I send emails from my personal account to Outlook users, they always end up in junk mail.
I presume this is because I send out a newsletter which uses my personal email, and some people press 'spam' instead of 'unsubscribe' when they no longer want to receive it.
Although I can tell individual people to add me to their contacts to alleviate the problem, is there anything else I can do?