Sending multiple emails (ie. newsletters)

I want to send multiple emails. I'm using MailMessage and SmtpClient. I know MailMessage.To is a Collection to which I can add multiple email addresses. I know an error will occur if the even one of those addresses is not in the correct format, so I'd like to know a couple of things below:



Does the object send emails one by one ie. does it perform checks on the email to addresses one at a time and if it's ok it sends the email or does it do a check all addresses before sending any email?

If one of the emails is not in the correct format, how do I handle this?
The script hasn't been written yet so no code to post I'm afraid.

Thanks
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