For the manual importation of OLM into Office 365, one has to first set up an IMAP email account-most preferably Gmail-in Outlook Mac. Move or copy all your OLM mailbox items into this IMAP account so that they sync to the server. Then, on Office 365 Outlook, create the same IMAP account and log in to download the synced emails. After the data shows, you can transfer it into your Office 365 mailbox.

The manual IMAP method has slow syncing, mailbox size restrictions, and the chances of losing folder structure or metadata. It can't directly import OLM files, multiple configuration requirements, and failed operations when it comes to large-sized mailboxes. It is time-consuming and involves procedures that are not suitable for users with little technical expertise.

Amongst the highly reliable and risk-free ways to migrate OLM to Office 365, the MacSonik OLM File Converter Tool is a prominent solution. This professional tool lets you upload single and multiple OLM files with 100% integrity of data into Office 365 mailboxes, public folders, and archive folders. Additionally, it supports the migration and conversion of OLM to IMAP Server, Gmail, iCloud, AOL, and other email clients from Office 365. This Aryson OLM Converter software will allow users to convert OLM files to PST, PDF, CSV, EML, HTML, DOC, etc. The software supports all versions of OLM files created in Mac Outlooks.

A Step-by-Step Guide to Upload OLM to Office 365 Using Software:
1. Download, install, and run the MacSonik OLM to Office 365 Migration Tool.
2. Then select the option Select File/Files and click Next.
3. Click the Select Files button to browse and add your OLM files.
4. Preview the added OLM files and click Next.
5. Choose which folders you wish to migrate and click Next.
6. From the drop-down list, choose Office 365 as the saving format.
7. Enter your Office 365 e-mail address and password to Sign_In.
8. Employ all other features provided by the software as may be required.
9. Click the Convert button to initiate the OLM to Office 365 migration process.
10. You can finally download the detailed report of the ongoing process.

Know More: https://www.macsonik.com/blog/import-olm-to-office-365-mac/