Internal Server Error - In accounts that were imported from another server

[riyadhali]

When importing mail accounts from an existing iRedMail server, following the necessary steps with folder names and other details, some emails with a few messages work fine. However, this message usually appears when trying to log in, with any imported email account:

Internal Server Error

The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.

all best

[riyadhali]

Task addition: An email account containing a few messages works without issues after being transferred along with the message folder. Accounts containing a larger number of messages encounter this problem:

The issue may lie in the message count limit. However, there is no limit to the number of messages as far as we know. I followed steps by deleting the dovecot.index.cache file, but I did not see any improvement in the result.
thanks