The expectation engendered by your subject line has a direct impact on response rates, according to this fascinating test, which sent the same email to a group of people, but with five different subject lines …seemingly a classic test of open rate.
Here's a fascinating test conducted by the people behind the Inbound Internet Marketing blog. In Set Expectations with Email Subject Lines they demonstrate how the expectation engendered by your subject line has a direct impact on response rates. They sent the same email to a group of people, but with five different subject lines …a classic test of open rate.
The five different versions all received similar open rates – but the clickthrough rates showed major variations. The reason? According to the authors, the subject lines which allowed the content to really deliver the promise were the ones which worked best. We should be careful about writing email subject lines which the email itself can't support.