As such there is no manual way to recover OLK14MESSAGE file of Mac Outlook until and unless one have specific knowledge about it and moreover not in knowledge till now.
OLK14 Message files are the raw files in which Mac Outlook stores your data in or you can say your mail database. earlier one uses OLM repair tool which is of no use as OLM is archived file format for Mac Outlook and does not lead to provide you accuracy all the time.
So, I suggest you to try OLK14 Message Recovery Tool. A tool which recover your mail database directly from raw files which are OLK14MESSAGE files either it is mails, contacts, calendars, attachments, etc. or any micro content in your mail database will be recovered if required. Moreover this is the only tool which also have a converter along which means you can recover your mail database and get them converted to other file format for any email client you like. It convert OLK14MESSAGE file to MBOX, OLM, EML, PST, Apple Mail, Postbox, Entourage, Thunderbird, etc. as it is and preserving your content and maintaining hierarchy of your folders and sub folders so you get exactly it was.
Try this OLK14 Message Recovery Tool as it is available with free trial version which will recover 10 files per folder and convert them if required. If you have lesser file to recover you may get them recovered in it's free trial version only as all the features are available in this mode.
For details: https://www.emailconvertertool.com/produ...