Home HubSpot Digital Marketing 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. personCertification Answers share Q. Fill in the blank: The ideal length of an email subject line is _____ characters. 41–50 55–75 10–20 75–100 Facebook Twitter Whatsapp Newer Older