How long should a subject line be? Stephanie Price-Bell May 24, 2017 15:48 Updated Follow DESCRIPTION: We recommend keeping your Subject lines to the point. Suggested Subject line length should be no more than 45 characters. RESOURCES: Check out our our blog posts regarding subject lines. Related articles What is Automation? Can I attach a file to a mailing? How does Send Rate Limiting work? Comments 0 comments Article is closed for comments.