When sending mass messages you are presented with two options:
Send as personalized message
Send as mass message
Sending as a personalized message will send the mass message as though it was a private one-on-one message, with no tells that it was bulk sent.
Sent as personalized message
Items sent as a personalized message will not include a subject and will show in the chat and emails exactly the same as any other message sent via the chat.
Sent as mass message
Items sent as a mass message will include a subject and will include styling around the message similar to mass messages sent for content release notices.
What format do I choose?
Certain messages should be sent as mass messages, and certain messages should be sent as private messages. Using the private message format sparingly will increase the effectiveness of that format. Here are some general rules of thumb:
Using the personalized message template as little as possible will increase its effectiveness.
Send major announcements using the mass message format only.
Use the personalize message template when targeting smaller groups.