Formatting email address

This line

mailMessage.To.Add(New MailAddress(txtTo.Text.ToString.Trim))

throws an error even when the content of the textbox is a valid email address. Substituting the textbox content for a string lteral IE email@domain.gov works OK. The error says the string is not properly formatted for an email address. So my question is: How do you format an email address? Also, if the textbox contains multiple addresses, how would you parse them out and add them?

 Thanks
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