Google Message Security for Google Apps Administration Guide - Manual (Page 387)

Customizing Notifications 387
For example, you should use the token for the “From” address rather than
hardcoding an actual support address. Then if you change the “Support Contact”
for your organization, you can be assured the change is be reflected in all
notifications sent to your users.
Wrapping Text around Tokens in Notifications
Once you determine what content your customized message should include for a
particular notification, you may simply compose the text and insert any tokens you
wish to use within that message. It is advisable that you use all of the tokens
supplied for a particular notification, since they all serve a relevant purpose for
explaining the nature of the notification. Otherwise, you can use virtually any
wrapper text that is relevant to your organization's needs.
To edit a notification, you may use either the editing window provided within the
Administration Console or upload a text file, the latter being more helpful for
allowing you to compose an HTML message and error check your composition as
well.
After you have edited your text or uploaded a file, your notification will be in effect
for your organization once you click “Save Text” from the text-editing window. Be
sure the text is accurate before proceeding!
HTML Editing for Notifications
If you wish to create an HTML notification, it may be easier to compose your
notification message in an external editor to error check the message, send the
message to yourself to ensure proper MIME encoding, and then save and upload
the finished file. This error checking of your composition beforehand is advisable
since HTML tags could potentially conflict with token tags if brackets are not
closed properly. You will also want to ensure your message will be viewed and
encoded properly.
Editing your notification in HTML allows you to insert links to external images that
you can host on your web site-allowing you to brand each notification with custom
graphics whenever the user receives and views the notification. For example, the
“Virus Alert” notification could include a red stop sign inserted.
HTML messages only differ from plain text messages by including HTML-specific
tags that enhance the impact of the message. Organizations that supply their
users with a web-based inbox will likely want to send notifications in HTML to
remain consistent with current branding, but it is not required to do so.
To include HTML content in notification messages:
1. Insert the following line at the top of the notify text:
Content-Type: text/html
2. On the next line start with the From, To, and Subject headers in plain text (no
HTML).