The instructor can send email to various constituents in a class.  The Various options are as follows:

All Users
Send email to all of the users in the Course.

All Groups
Send email to all of the Groups in the Course.

All Teaching Assistants
Send email to all of the teaching assistant users in the Course.

All Student Users
Send email to all of the Student users in the Course.

All Instructors
Send email to all of the instructor users in the Course.

All Observers
Send email to all observer users.

Single / Select Users
Select which users will receive the email.

Single / Select Groups
Select which Groups will receive the email.

Single / Select Observers
Send an email to selected observer users.

To Send E-mail

Option 1

From Course Menu

1. Select Communication.

2. Select Send Email.

3. Choose Recipient.

4. Type Subject and Message.

5. Select Return Receipt, if desired.

6. Click Submit to finish.

Option 2

From Control Panel                 

1. Under Course Tools , select Send Email.

2. Choose recipient. 

3. Type Subject and Message.

4. Select Return Receipt, if desired.

5. Click Submit to finish.

Note:  Using the e-mail though Blackboard is not a recommend function because there is no way to confirm or guarantee delivery.