Older emails missing

I’m using 4 separate email addresses with eM Client. 3 on the same server on my own domain on IMAP and a separate POP3 account. Since the recent update I’ve noticed on 2 of the addresses, all emails older than 18 months ago on one and 2 years ago on another of the IMAP addresses have disappeared, while all remain in eM Client on the third. Can you tell me what’s happened to the older emails on the other 2 addresses and how to retrieve them, please?