Home - HubSpot Digital Marketing Course - Fill in the blank: The ideal length of an email subject line is _____ characters. Fill in the blank: The ideal length of an email subject line is _____ characters. 2shares Facebook Twitter Pinterest LinkedIn Skype Facebook MessengerQuestion: Fill in the blank: The ideal length of an email subject line is _____ characters. 41–50 55–75 10–20 75–100 The right answer was: 41–50