no sent email sound, what is the repair solution?

Assuming sounds are otherwise ok on the computer, try a PRAM reset.

• Shut down your Mac.
• Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
• Turn on the computer.
• Press and hold the Command-Option-P-R keys before the gray screen appears.
• Keep holding the keys down until the computer restarts and you hear the startup sound three times.
• Release the keys.