Hello, We have MBOX mails sized by 46,321,930 KB and exported from Gmail account to store and save to see anytime. I understood this MBOX file only can be opened and see the contents through Thunderbird. We have a few questions to use this program properly. See the questions below and answer, please. 1. This file has been imported and visible with the same file name and the quantity of the 30,044 emails sign. However, the contents are not shown up after we click the file through Thunderbird. The contents were actually popped up a few days ago and currently are not visible at all. Please explain this happening and let us know how to manage these contents to check. 2. Even though we make these MBOX files imported in the Thunderbird program, we couldn't make sure that it is possibly open to see since it has disappeared in the program as said in a 1st question. We currently have this MBOX mail in the computer and would like to keep it in an external hard drive to open this file to see in the future. We wonder if it is possible to import anytime and on any device if they download the Thunderbird program and have the same MBOX file.   3. We are not familiar with the MBOX format, and Google didn't let us export the whole quantity of the 64GB emails (there are missing emails in specific beginning periods which are not able to be seen as the same as the emails at the Gmail account). We would like to know if we could trust this MBOX and Thunderbird program with no more missing emails.  We might need to make a call to discuss more about the program and the file after checking your response. Thank you. Best regards, Stella