To merge EML files into a single PST file you can take help of Mailsware EML to PST Converter Software. The tool enable to convert EML files to PST with attachments in bulk. It comes up with easy user interface and capable for quick migartion.

Features of the tool

• Merge thousands of EML file to single PST file
• Move Non-English EML text to PST format
• Save resultant file to the desired path 
• Convert EML files to Outlook as well Exchange server easily
• All Windows OS and Outlook versions supportive

Try the demo version Now! http://www.mailsware.com/dl/mailsware-eml-converter.exe

Recoveryfix for MBOX to PST software is developed with an advanced option to browse and add several MBOX folders at a time to perform migration into the desired file format. Few notable features:

1. Add a Folder Contains MBOX files
2. Convert several MBOX files into PST, EML and MSG.
3. Preview Emails with intact Mail Properties
4. Preview and Export Email Attachments
5. Easily export MBOX file to Office 365 Account
6. All Outlook Versions Supported

Read more : http://mboxtooutlook.blogspot.com/2016/12/how-to-migrate-data-from-mbox-to-office-365-platform.html

OR

http://www.recoveryfix.com/mbox-to-pst-converter/

PST to MBOX Converter (http://www.mozesoft.com/outlook-pst-to-mbox-converter.html) for Mac tool to convert Outlook Emails and their attached files to Mac Mail. Free Online PST to Mac Mail Converter can easily online purchase from our website with safe and secure procedure. Additionally import Emails, Contacts, Calendar, Tasks, and Journals etc. from MS Outlook to Apple Mac Mail. - See more at: https://softcart.wordpress.com/outlook-pst-to-apple-mail-mbox-file/