Yes, splitting a large MBOX file can be safe when the process is performed with a reliable tool and the original file is preserved as a backup. The main concern is whether emails, attachments, formatting, and metadata remain intact after the split. This is where SysTools MBOX Splitter can be useful for users dealing with oversized mailboxes. It is designed to divide large MBOX files into smaller files while retaining email content and attachments, helping reduce the problems that can occur when email clients struggle with very large mailboxes.

For anyone wondering is splitting large MBOX safe, a few precautions are still important:

Keep the original MBOX file: Always create a backup before starting the splitting process so the source remains available if something unexpected happens.
Choose an appropriate split method: SysTools allows MBOX files to be divided by size, date, date range, year, sender, or subject, making it possible to organize the resulting files according to the actual requirement.
Check the output: The software provides an email and attachment preview before splitting, which can help verify the source data before processing.
Preserve important content: According to the product documentation, the splitter retains emails, attachments, sender/recipient details, formatting, links, subjects, and date information during the process.
Reduce oversized-mailbox problems: Smaller MBOX files can be easier for compatible email clients to handle, particularly when a large mailbox causes slow performance or access issues.

Therefore, is splitting large MBOX safe depends largely on the method used and whether proper backups are maintained. For large or difficult-to-manage MBOX files, a purpose-built splitter can make the process more controlled while reducing the risks associated with manually modifying mailbox data.