When sending from primary (Earthlink hosted) mail account, mail goes to Sent mailbox and proper sound is made, but the mail is not delivered to sender. Gmail account does not have a problem from the MacBookPro--only the Earthlink-hosted account. Using the same Earthlink-hosted mail account, this problem does NOT occur from iPhone 5. Using a different Mac, no problem there, either. Earthlink has verified that all settings are correct. With help of senior Apple tech, have reinstalled OSX and upgraded back to 10.6.8. Deleted and reinstalled the troubled mail account. They have also verified that all settings are correct, but it doesn't work. They've submitted to engineering for a solve. Anybody else have this challenge? Thanks!