Here is the relevant part of my sieve rule. Just know that you can switch the :contains to :is this would make it so the localpart would have to match the sender domain exactly. I'd do this but I initially wasn't using the full dns name for my localparts:

# Account sorting set "domain_name" "acct.ninja"; if address :domain "To" "${domain_name}" { if address :localpart :matches "To" "+" { set :lower :upperfirst "addr" "${1}"; set :lower :upperfirst "subaddr" "${2}"; if not address :domain :contains "From" "${addr}" { fileinto :create "SPAM"; } else { fileinto :create "INBOX.Accounts.${addr}.${subaddr}"; } stop; } elsif address :localpart :matches "To" "*" { set :lower :upperfirst "addr" "${1}"; if not address :domain :contains "From" "${addr}" { fileinto :create "SPAM"; } else { fileinto :create "INBOX.Accounts.${addr}"; } stop; } }

Sure. Check back in a day or two. I'm on vacation, and don't have my computer with me atm