Many email clients support a second piece of descriptive data beyond the subject line. This is usually known as the pre-header, and is a bit like the description line after the headline of a search result. GMail users will instantly know what I mean, but here’s an example if you’re unsure. So the user of an email client which supports pre-headers doesn’t just see the subject line in their inbox, but some more text too.
Setting up pre-headers is a feature in most mass-mailing software, such as Mailchimp. But in everyday emails, you don’t get the chance to add this text. So if it isn’t specified, what do recipients see in an email client which shows the pre-headers? GMail users will know: it’s the first few words of the actual email. And on a large proportion of mass emails, that’s something very disappointing such as “View this email in your browser”.
Don’t make this mistake. If you can set the pre-header in your mailing software, do take the opportunity. if you can’t, make sure your email is constructed so that there’s something useful in the first few words, not “View this email in your browser”. This email is an example.