Big Incremental Backup over thunderbird local mail (mbox files)

We are using UrBackup 2.2.11.
The incremental and complete backup files over thunderbird forlder are equal, despite to have configured set the local transfer mode of incremental backups to “block differences - hashed”, according with mentioned at Special treatment of .pst files (not .ost files)

Thanks for your help.

Which size are you using? The one from a incremental backup log (on the server web interface)?

Yes, the one from web interface

Hi everyone,
has this issue been solved? I am having exactly this problem - incremental backups size = original backup size. It is consuming much space on backup server. The initial full size backup of thunderbird folder is 17GB (terminal). Each incremental directory has the same ± 16/17GB. Is there a way to get incremental backup only new or modified files? UrBackup Server v2.4.13.0 on Debian 10, filesystem ext4. Client is Windows 10 pro, thunderbird mail client, imap. I am backing up path “c:\Users\user\AppData\Roaming\Thunderbird\Profiles”. Client version is ± 1 month old, can’t verify now as client is out on business. Zip file with xlsx data attached. (6.2 kB)
Thank you much for any help.