jrao/liferay-docs — comment on commit a9474386246ce526289c2af7592d903ff3df35ce
File: userGuide/en/chapters/04-liferay-collaboration-suite.markdown line 1020
By sergiogonzalez:

Actually it's not the User Id, it depends on the login configuration of the portal (it could the the userId, but also the screen name or the email address). By default it's the mail address.