mailto:me@nowhere.com?Subject=You must buy these books!
    &Body=Prototyping with Visual Basic%0D%0AVisual Basic G
    raphics Programming%0D%0AReady-to-Run Visual Basic Algo
    rithms%0D%0A

The HttpUtility.HtmlEncode method converts a string into an HTML-encoded string, replacing special characters with hex values and so forth.

Next the program makes a ProcessStartInfo object specifying IExplore.exe as the program to start and the mailto command text as an argument for the program. Finally it uses Process.Start to start IExplore.

' Compose the command string.
Dim txt As String = ""
If txtCc.Text.Length > 0 Then txt &= "&cc=" & txtCc.Text
If txtBcc.Text.Length > 0 Then txt &= "&bcc=" & txtBcc.Text
txt &= "&subject=" & HttpUtility.HtmlEncode(txtSubject.Text)
txt &= "&body=" & HttpUtility.HtmlEncode(txtBody.Text)

' Remove the initial &.
If txt.Length > 0 Then txt = txt.Substring(1)

' Add the To addresses.
txt = "mailto:" & txtTo.Text & "?" & txt

' Start the default mail system.
Dim start_info As New ProcessStartInfo("IExplore.exe")
start_info.WindowStyle = ProcessWindowStyle.Maximized
start_info.Arguments = txt
System.Diagnostics.Process.Start(start_info)