Mozilla Thunderbird only supports MBOX file format but due to lack in features many users are moving from Thunderbird to other email clients but they didn’t know that MBOX files are not supported by all email clients. If you are willing to shift from Thunderbird to Gmail then you can do so with the help MBOX File Converter software. This software will help you to export MBOX file directly to Gmail Account.
All you have to do is to provide the credentials of your Gmail account and directly import MBOX file into it. This software is embedded with some features like Date Range and Name Convention. The Date range feature allows the user to search MBOX file on the basis of date. On the other hand the user can also rename the resultant files according to his convenience. So it is totally your decision whether you want to avail the tool or not.