Why Do Emails Sent In Mac Mail Not Appear In My Sent Folder?

When using IMAP, Mac Mail requires you provide a specific folder to save sent messages. Follow these simple steps to configure this:
  1. Click and highlight the Sent folder for your account
  2. Click the Mailbox menu
  3. Choose Use This Mailbox For
  4. Choose Sent

This will configure Mail to save new outgoing emails to the sent folder for your account. If you want your previously sent emails to appear they must be dragged from Mail's local sent folder to the sent folder listed under your account.