This AppleScript will parse the selected e-mail in Mail.app for UPS tracking numbers and will open the tracking page of the UPS website in your default browser.

This only looks at a single e-mail, but could be made to repeat through multiple selections.

tell application "Mail"
set _messages to selection as list
set input to content of item 1 of _messages
try
open location my parse_nums(input)
on error
display dialog "No UPS tracking info found."
end try
end tell

on parse_nums(input)
set input_new to ""
set output to ""
set input to every word of input
repeat with i in input
try
if first character of i is "1" and second character of i is "Z" then --Every UPS # I've seen starts with '1Z'
set input_new to input_new & i & "%0D%0A" as string --
URL encoded carriage return line feed needed for multiple entries.
end if
end try
end repeat
-- Now to remove the last set of new line characters.
repeat with c in characters 1 through ((count of characters of input_new) - 6) of input_new
set output to output & c
end repeat
set the_URL to "https://wwwapps.ups.com/WebTracking/track?track.x=Track&trackNums=" & output
return the_URL
end parse_nums