''Colleagues'' column with different domain

''Colleagues'' column with different domain

Hi, 

In my company we have 2 emails domains, @domain1 and @domain2.
My problem with Salesinbox, is all the emails I received from my collegues with the @domain2 aren't showing up in the ''Colleagues'' column, but in ''Contacts & Leads'' instead.
How can we fix this.

Thank you,