The best way to convert Outlook OST email to Gmail is to use the professional tool like Aryson OST to PST Converter . Why I'm recommending you this tool because this tool converts the OST file into multiple file formats like PST, PDF, DOC, DOCX, HTML, MBOX, etc. It also helps to maintain the data hierarchy through out the conversion process and transfer the OST file to the number of email clients like Office 365, Thunderbird, Yahoomail, Gmail, etc. This tool easily converts the OST file with attachment in bulk. However, this tool maintains the data hierarchy through out the conversion process. It comes with the best GUI that makes this tool easy for everyone. 

Easy Methods To Convert Outlook OST email to Gmail

- Download and install the OST file converter in your system. 

- Then select the OST file to convert and click next. 

- Now select the file and folder to preview and click on the next button. 

- After this select the file format in and set the path to save the resultant file. 

- Now click on the convert button to start the converison process. 

Well, if any user wants to read the other method to convert OST file then read this article 3 Free Methods to convert OST to PST.