The summary is used to display the list of mails in the user interface. That is is always invalid leads me to think you are using something one drive to synchronize files and therefore the summary is always unavailable, or you have an anti virus product that is scanning and locking files.

As for your apparent second issue, The filter can not act on a message until it can see it. so it must be downloaded to the local drive (the temp folder is the usual first destination for a message that size) and then filtered into it's location. Non all actions occur in memory.

The summary is used to display the list of mails in the user interface. That is is always invalid leads me to think you are using something one drive to synchronize files and therefore the summary is always unavailable, or you have an anti virus product that is scanning and locking files. As for your apparent second issue, The filter can not act on a message until it can see it. so it must be downloaded to the local drive (the temp folder is the usual first destination for a message that size) and then filtered into it's location. Non all actions occur in memory.

I tried to turn off the antivirus and monitoring software, but the problem still occurred. Is it related to the capacity of the mail folder? PS: The local directory of the email client has used 280GB, and a single folder uses about 8GB.

A good starting point might be to compact all folders. It is on the file menu because U really doubt you have anything like 200Gb of mail. A compact will re-download most of the IMAP mail, so expect a large hit to downloads.

A good starting point might be to compact all folders. It is on the file menu because U really doubt you have anything like 200Gb of mail. A compact will re-download most of the IMAP mail, so expect a large hit to downloads.

The email client uses the pop mail, not the IMAP mail, and the mail is stored in a local directory. Because it has been used for many years, the total amount of mail in the local directory is 280GB.

In addition to compiling summary files, searching for email keywords is also very slow, and even crashes.

I use importExportTools NG for mail import. I do not know if there is a problem during the import?

Try this :

Where is the location of the mbox you want to import?

If on One Drive or similar suggest you restart computer in 'Safe Mode with Networking' option.

then start Thunderbird

When importing - second image - try selecting the first option - Import directly one or more mbox files, and click on OK

When window opens, locate and select the mbox file and click on Open

Wait a while as it is a single document - a file - of substantial size.

I would suggest you create some folders and organise emails into those folders. This will reduce the file size for the mbox files and it is less risky than having so many emails in so few files.

Try this : Where is the location of the mbox you want to import? If on One Drive or similar suggest you restart computer in 'Safe Mode with Networking' option. then start Thunderbird When importing - second image - try selecting the first option - Import directly one or more mbox files, and click on OK When window opens, locate and select the mbox file and click on Open Wait a while as it is a single document - a file - of substantial size. I would suggest you create some folders and organise emails into those folders. This will reduce the file size for the mbox files and it is less risky than having so many emails in so few files.

First, the program is in C:\Program Files (x86)\Mozilla Thunderbird, in the account settings-server-local directory D:\Email\XXX, MBOX is saved in D:\Email\XXX.

Second, why should I restart the computer with the "Safe Mode with Networking" option?

Third, there are too many folders originally created, there are three layers of folders in the local directory, for example: D:\Email\XXX\ (custom folder)\ (custom folder), each custom folder There are MBOX inside. As I mentioned before, the size of the local directory is 280GB, so it takes a long time to import using the first item when importing.

Fourth, there is another new problem today(pictured), the system prompts that [folder "(custom folder)" cannot be compressed. Because an error occurred while writing to the directory. Please make sure you have enough disk space and you have write permission to the file system, then try again. ], then rushed to exit. After inspection, the hard drive has 300GB unused.

Ultimately, I need to find the cause of the problem and the solution to the problem.

           For example: 
           1. Is the setting wrong?
           2. Are installation and operation errors?
           3. Are there missing plug-in tools?
           4. Are there compatibility issues?
           5. Other reasons.