If you wish to send an email message to multiple email addresses, then you need a way to address the email. For example, you may be emailing to and fro with a colleague, and wish to include another person in the conversation. Or, you may wish to send your travel plans or party invitations to all your friends and family at the same time.
In the To: field of your email programme, you can enter as many email addresses as you like by separating them with commas.

In Thunderbird (the email programme that I am currently using), you can press ‘Enter’ on your keyboard to give you another space or field to type in another email address.

Depending on the purpose of your email message, you may wish to use the Cc: (courtesy copy) or Bcc: (blind courtesy copy) email address fields.
Think of Cc: as the carbon copy or courtesy copy that you provide to others for their information, rather than their action. The person that you addressed in the To: field is the main recipient.

For privacy, you may use the blind courtesy copy. This way, none of the people who you send the email to will see the other addresses added in the Bcc: field; only their own and the person you addressed the email in the To: field. This is the polite way to do things so you don’t disclose people’s email addresses without their permission.
Make the To: field your own email address if you do not wish any of the Bcc: recipients to see any email addresses except yours and their own. Note: You will get a confirmation copy back yourself, of course, because you listed your own address in the To: field.

The same way you listed many addresses in the To: field, you can list them in the Cc: and Bcc: fields.
If you will be sending the same email message to a group of people, you may wish to set up their email addresses in an address book.



