To invite someone, click on the 'Invite a friend to join Gmail!' link in your inbox. You will then be asked to provide an email address and a personalized message to your invitee.
The person you invite will be sent a message that includes a link to join Gmail. That registration link will be valid for three weeks and can be used to create only one account.
Please note that the link may not always be available. When you are allowed to invite others to join Gmail, the number of invitations that you can send will be indicated at the top of the page after you click on the link. Once you have used all of those invitations, we will not be able to immediately issue more invitations.