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January 27, 2009

Another Look at Email Subject Line Length

Epsilon recently published a study on the importance of the subject line in email promotions. Overall the report confirmed the widely held belief that shorter subject lines performed better but concluded that the correlation was not as strong as previously believed.  Other critical factors affecting click and open rates were subject line word order, word choice, and brand and audience awareness.

More importantly to email marketers, Epsilon found that email domains like AOL, Yahoo and Hotmail restricted the number of subject line characters displayed by default. Character limits ranged from 38 characters for AOL to 47 for Yahoo with Hotmail coming in at 45. Together the 3 web-based mail providers control 57% of the US market ensuring that email recipients at those services see only truncated message subjects.

Epsilon’s analysis of more than one billion emails over nearly 20,000 separate campaigns led them to recommend that email marketers keep the following in mind:

  • Front load subject lines. Important information first.
  • Keep the subject line as short as possible.
  • Use longer subject lines only when necessary.
  • Test, if in doubt.

The complete whitepaper can be viewed at: