Mac Mail inbox only displays current month.
I have a new iMac with Catalina (mail 13.4). I have an email account which was POP on my old Mac that I have had to set up as IMAP on the new one. Trouble is on the new Mac, I can only see messages for the current month. I've resent some old messages again from the old Mac to the new one, so they should be stored on the server, and indeed they appeared last month (March 2021) but now we are in April they no longer appear. How can I get the inbox to display all the messages on the server. My other email accounts are fine (but they were set up as IMAP on the old Mac).
Thanks in advance.
David