To keep my IMAP account's inbox as small as possible, I move mails into yearly archives. I usually do that once every quarter. But if I don't, well then I have many mails to move. This AppleScript does the heavy lifting.

Archive.scpt

tell application "Mail"
	set _a to imap account "sc@itst.net"
	set _i to _a's mailbox "INBOX"
	set _ms to (messages of _i)
	set numLog to 50
	set iteration to 1
	set iterationMax to number of _ms
	log iterationMax & " msgs to move"
	repeat with _m in _ms
		if (iteration mod numLog is 0) then
			log iteration
		end if
		set _rd to date received of _m
		if (year of _rd is 2019) then
			move _m to _a's mailbox "z-Archiv/2019"
		end if
		set iteration to iteration + 1
	end repeat
	synchronize with _a
end tell