Preheader
From EtelligentWiki
A pre-header is a block of text that appears in your email before your branded masthead. It is designed to exploit preview features in modern email clients called snippets.
Most marketing emails -- by convention -- carry a "view in browser" prompt as the very first piece of text in the message. With the advent of snippets, this is a missed opportunity; in these cases, the snippet preview a recipient sees (such as a pop-up alert in the taskbar with Outlook) will actually tell them nothing about the email.
The content of a pre-header should be a sentence or two that summarises your email's content.
Pre-header example
The blue strip across the top of the below email holds summary information about the its content.
(Click the image below to see a larger version.)
This pre-header's text would then appear for recipient as something like the below screenshot (Outlook 2007):
This preview is called the snippet.
Pre-header content
Snippets popping up in a user's taskbar give you about 3-4 seconds and up to 100 characters to prompt them to open your email. Depending on the proposition of your message, you may opt to go with a single short sentence or a short list of key words.
Outlook and GoogleMail also support snippets at the user's inbox. The available text shown in the preview is even shorter than the pop-up at around 50-60 characters.
