Imported mailboxes/mail folders: (1) Number of messages shown in imported mailbox less than number shown in finder window; & (2) Log of what was & wasn’t imported

When I import certain mailboxes, the number of messages shown is less than the number shown in the corresponding finder window (through a Spotlight/Find search for ‘Kind: Mail Message' or 'Name contains: emlx'). Is there a way to fix this, or a reason why it’s taking place?

Also, Console wasn’t much help as far as finding out what was & wasn’t imported. Is there some other way or Apple log to identify which what-appeared-to-be messages were not imported, & why? Is there a log that specifies which messages were imported?

All of the messages originated as some kind of Mac Mail.

Also, I’ve done a rebuild of the mailboxes and deleted the appropriate library data files beginning with the word ‘envelope’ numerous times.

Thank you!