Sometimes your organisation will assign an alias - this can be done for a number of reasons which you can read about here.
This can cause a little trouble if you haven't accounted for it when setting up Hiri. Hiri will treat it as a different email address. This has an annoying side effect - every time you reply to an email, you will see your email at the top of the conversation, because Hiri will think it's a new mail from a new recipient on the thread.
Here's how to add an alias to prevent this from happening.
Go to Settings -> Account and scroll down to the Alias Addresses section:
Just add your alias email address here and hit Save. That should do the trick!