Mail no longer puts commas on multiple e-mail cut and paste

Occasionally I send out an email to hundreds of e-mail address's.

I generally send 30 at a time.

I copy them from my Bento list and put them into the BCC box.

It the past Mail always put in a comma to separate the address's.

In othe rwords after the .com

This is the first time I am sending them under Maverick and the commas are gone and the warning comes up that the address's is unacceptable.

Obviously because of the comma's missing.

Is their a way to do this, other then going in and putting a comma after every address?