Alas ~ ~ this kind of situation will happen to anyone. You want to save space and save your mail. I suggest you back up to another disk. This can speed up the cleaning and keep the mail.

You open OE, then you have an option in the tool, and then you choose Maintenance. There is a storage folder in the maintenance, and all the letters in the village folder are OE letters. You can copy this file to another disk, and then delete it. Remember to delete the entire OE directory, and then restart OE. It will automatically generate an OE folder, and the contents will be gone. Then, after selecting Enter, each letter can be re-entered, which is very convenient.

This can barely achieve your goal ~