Hi @Mike Accola ,
According to your description, here are 2 methods for you to migrate old mails to outlook 365.
- Export old mails to .PST files and import these into outlook 365.
- Manually copy or move the old mails and the Email folders to outlook 365.
Detailed step by step guidance for your reference: How to Transfer IMAP or POP3 Emails to Office 365 using Outlook.
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