[exim] SMTP Multiple Recipients?

Trying to understand the smtp protocol with multiple recipients. From
what I understand the recipients are specified as follows:

rcpt to:person1@???
250 Accepted
rcpt to:person2@???
250 Accepted
rcpt to:person2@???
250 Accepted

Suppose I'm doing forward callouts to verify recipients. And suppose
person2@??? is a bad email address. How should the server respond
to say that there is one bad address but 2 are ok?

Thanks in advance.