When you find it by searching, where is it? POP or IMAP account? Where are sent messages stored, according to Copies & Folders in Account Settings?

The search is in the sent folder and that's where it is found. It is a POP account. Copies are placed in the SENT folder of the Earthlink.net account via the Settings for copies.

How are searching, Classic (Ctrl+Shift+F) or Global (Ctrl+K)? If it's Global, see if you can find it with Classic. The reason is, Global might 'find' a message that was deleted if the search index is obsolete.

I am using the "classic" search from the "Edit" drop down menu. I have not used the "ctrl K" search on email.

Try Repairing the Sent Mail folder on your Earthlink Account. In the Folders Pane on the Left find the Sent Mail folder in your Earthlink account. Right Click on the Icon of the Sent Mail folder (still in the Folders Pane on the Left) and Choose Properties. Click the Repair Folder button then Click OK. (Wait a while for repairs to finish ... ) Look again to see if some messages are still hiding from you, OK? I bet they have all come back now.

Repair of Sent file worked. The missing email is back. Thanks for all of the help.

You are welcome.