I need to parse HTML for emails, but its not working right

I have a code, that searches for emails. But when I load in the source code with html and all the emails inside, It doesnt spit out all the emails. Can someone help or improve my code?

Code:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim emailString As String = RichTextBox1.Text
        Dim emailRegEx As New Regex("""(\S+)@([^\.\s]+)(?:\.([^\.\s]+))+", RegexOptions.IgnoreCase)
        Dim m As Match = emailRegEx.Match(emailString)
        If m.Success Then
            Dim output As String = ""
            output &= "User name: " & m.Groups(1).Value & vbCrLf
           
            RichTextBox2.Text = output

        Else
            MsgBox("The e-mail address cannot be parsed.")
        End If

    End Sub

 

Instead of using Regex, just use a simple function to get between two strings...So if the email is between let's say a <frame> tag and a <font> tag, then you could grab it and display it where you need to. If you search "GetBetweenAll" on Google you'll come across a few decent sources.