Sorry but in res.user there is not field usr_email.. (I'm talking about V7.0)
In PGAdmin you can see those fields for Res.user :
id serial NOT NULL,
active boolean DEFAULT true,
login character varying(64) NOT NULL,
password character varying(64) DEFAULT NULL::character varying,
company_id integer NOT NULL,
partner_id integer NOT NULL,
create_uid integer,
create_date timestamp without time zone,
write_date timestamp without time zone,
write_uid integer,
menu_id integer, -- Menu Action
login_date date, -- Latest connection
signature text, -- Signature
action_id integer, -- Home Action
alias_id integer NOT NULL, -- Alias
share boolean, -- Share User