If you do not tag someone in a message, the recipient should still receive an email of the message as long as the email notification settings are on.
The default for all Anvyl users is to receive email notifications for all messages, including those they are not tagged in. The recipient of the message will not receive the email notification if those settings have been changed or turned off.
Note: If anyone has changed their email settings to only be notified when tagged, they will not receive the email notification.