Expand email to activity to support other contact types besides Individuals

An organisation contact was set up, with an email address. An email was sent to this organisation, copying the email address set up as the 'email to activity' mail account. However Civi did not record the activity against the organisation, but created a new contact record (an individual) with the email address of the organisation.
Oddly, this is not consistent - sometimes it works correctly. I have marked this as major as this is a feature my user is depending on for recording fund raising bids.
This is a Drupal system.