c#: send mass mail with BCC: "To" field is not filled

Question

For sending mass emails I use single instance of MailMessage class and filling it Bcc property with collection of addresses. However when mail comes, its "To" field is not filled.
I've got two questions:

1. how can I make "To" field filled with appropriate address?
2. how sending single message to multiple recipients with Bcc field compared to sending multiple messages addresses to single recipient in terms of performance?

Answer 1

1) You can't, unless you send each mail individually which brings me to 2)

2) sending one message with multiple bcc recipients means you're only sending one message. this will be obviously much more performant than sending multiple messages, as mentioned in 1)

Of course, once you've flooded the listening SMTP server with messages you are at the mercy of your ISP to allow you to spam, which is highly unlikely. Stick with your current situation if you want to have a simple life :)