Is there a threshold when emailing a group via workflow?

I created 2 groups in SharePoint 2010. One has approximately 20 users and the other has 1600 users. I created a workflow that uses Group 1 (20 users) in the BCC field to send an email to this group. It works fine. When I edit the workflow to send the email to the larger group (same permissions), it does not send the email. Is there a threshold for how many members it may email?

Thanks!