It’s an ongoing debate, but research from MailerMailer.com and MailChimp.com has hard evidence to show just how long the perfect subject line should be to get both the highest open and the highest click rates.
The magic number sits between 28 and 39 characters and has shown clicks at 4% on average and open rates at 12.2% so stick to around 28 to 39 characters (but don’t be too scared to step a little outside this range).
A quick bonus tip is to AVOID personalisation in those subject lines. Research from MailerMailer.com actually shows a significantly lower CTR on personalised emails. It’s not clear why this is, but one reason could be that these personalisation techniques are being used more and more by spammers and therefore the general public are associating personalisation with spammers.