When you create a new e-mail message based on .oft template in Outlook, you will get it saved in a .olm file, which pretty much covers the process of oft to olm conversion. But this only works in macOS/ OS X version of Outlook, which is actually the version that uses .olm files to store e-mail data.
Open OFT file Open OLM fileMac version of the popular e-mail client and personal information manager from Microsoft