Is there any trusted method? 

The easiest way to open a Gmail Takeout MBOX archive is by using a dedicated viewer like MacSonik MBOX Viewer. When you export your mailbox through Google Takeout, the emails are saved in an MBOX file, which cannot be easily read without a compatible tool. Using MacSonik MBOX Viewer, you can simply add the Gmail MBOX file to the software and instantly preview all emails in a structured view.

The tool scans the MBOX archive and displays each email along with its attachments, subject, sender, and other details. It also provides different preview modes such as Normal View, Message Header, Hex View, and Properties, which helps you analyze the email data more clearly. Another advantage is that it maintains the original folder hierarchy and formatting while allowing you to open large Gmail Takeout MBOX files without any size limitation. Because it works independently and does not require configuring an email client like Mozilla Thunderbird, it becomes a quick and convenient way to read emails stored in a Gmail Takeout MBOX archive.