You can configure event reminders to be sent to volunteers 2 days before, 1 day before, or right after the event.
Once you are logged in go to Event Sign-ups
Find your event in the calendar and click on it to edit.
At the bottom of the page, locate the Manage section and select Edit.
Check which notifications you would like to send to your Volunteers
At this time there isn't a way to send out customized emails to specific volunteers. If they provide their email during sign up, you can copy their email address into your emailing provider and send messages that way.