Go into the Sent Folder, and in the bottom left, there will be an icon that looks like a circular arrow. That's the refresh button.
Also, go into your Mail Settings (where you set up your mail account), into the specific mail account and look under Advanced settings. Depending on the paid provider, you may have an option for saving sent emails.
If all else fails, in that Mail setup screen that lists your mail accounts, there is a general option to "Always bcc myself". Turn that on. Every email you send will also be sent to you. A little bit of a pain because now you'll get extra emails in your inbox, but you'll at least have a copy of the email.