Is there a way to determine how many outgoing emails GW can process ?

Say over a 8 hour period.

I have a client who wants to send out 3000 - 4000 emails once a month
last time time they tried they ended up with 600 out of 2700 emails
being returned as NDR. All the email address are varified.

(one email - multiple recepient)

I have suggested they use a email marketting company.... but they are
reluctant to
pass on email addresses to 3rd party.