Events linked to wrong email address

Hi,

I have Outlook which has 3 email addresses:

- Personal email (@hotmail.co.uk)

- University email (Microsoft exchange)

- Students union email (Gmail)

When I respond to a meeting sent to the students union email it appears in the calendar under my personal email address. How can I stop this from happening?

Also, I cannot seem to get the students union calendar part to show within Outlook - any advise on this?

Thank you.