Preheaders are small phrases (up to 80 characters) that should help increase your click-through rate. Many email clients display the first letters of an email in their preview area.
Preheaders are invisible in the normal email view and show up only in the preview pane of some clients.
Preheaders in Mailster
Mailster allows you to define the preheader of your campaign in the details meta box. You can use emojis here as well.
