Check out Advik OST File Converter. This tool is specially designed to upload .ost data into various email service provider including Zoho Mail. You can import OST to Zoho Mail without Outlook. The tool is powerful enough to upload large .ost file without facing any glitch or error.

Step 1. Run Advik OST Converter and click Select Files.

Step 2. Add Outlook .ost file and click Next.

Step 3. Choose IMAP as export option.

Step 4. Enter your Zoho Mail login credentials.

Step 5. Click Convert to start the migration process.

That's it. This is how you can import OST to Zoho Mail to import Outlook Offline data. 

Free Download: https://www.adviksoft.com/dl/advik-outlook-ost-converter.exe

Switch to Zoho Mail Now.

Note: Below are the IMAP settings (for Reference)