Ford returned to work June 30 after a two-month stint in rehab for drugs and alcohol. He admitted last year that he had smoked crack in a "drunken stupor."
Ford said he didn't consult with police before going public with the email threat that was sent Sunday night to his brother, city councilor Doug Ford. Rob Ford read and showed a copy of the typo-ridden email to reporters. He later continued with meetings at City Hall.
Toronto Police spokesman Mark Pugash later said a search by police found no evidence of any explosive devices.
Ford is seeking re-election Oct. 27.