PHOTO: Adobe Subject lines are the first thing recipients will see in their inbox. According to Invesp, 47% of email recipients open an email based on the subject line. If the subject line doesn't do its job, your recipients won't ever see the message. The subject line is an important aspect of email marketing because it needs to grab the recipient's attention and compel them to open your message, leading to a sale or conversion. Not only does your subject line need to be compelling it also needs to align with the content of the message you are sending. A good subject line should grab attention and make the reader want more. Shorter is better for emails because you want your message to come across quickly.