Can't select a message using AppleScript

[John Delacour]

The script below runs without error but fails to select a
message. Is there a good reason for this? If I replace
<select> with <open> then I get what I ask for.

tell application "Mailsmith"
activate
set index of window "Mail Browser" to 1 --OK
--select mailbox "(incoming mail)" -- OK
select incoming mail -- OK
select first message in incoming mail --!! No selection results
end tell

--JD

PS. The script I posted for sending a message with a Return
Receipt request has worked well ever since.