I manage multiple Thunderbird accounts for a small business, and manually exporting every folder is becoming incredibly time-consuming. I'm hoping to find a solution that can transfer an entire mailbox in one go without causing downtime.

The MacSonik Thunderbird Backup Tool  claims to support bulk mailbox migration while maintaining data integrity throughout the process. It can migrate Thunderbird emails directly to Gmail, Office 365, IMAP servers, Yahoo, Zoho Mail, AOL Mail, Hotmail, iCloud, and several other destinations.

It also allows users to choose a custom destination path and filename for exported data, which makes organizing client backups much easier. From what I've read, the software is compatible with modern macOS versions including Monterey, Ventura, Sonoma, and later releases.

Minimal downtime is another feature that interests me because some of these mailboxes are actively used during business hours.

If you've migrated an entire Thunderbird mailbox with this utility, how was the overall experience? Did it successfully process very large mailboxes without interruptions or missing folders?