How to tell if a Cashier s check is fake?

YOU and your bank have NO way to check if a cashier's check is fake. ONLY the issuing bank can check it.
If the issuing bank has a branch in your city go into that bank with the original check and ask them to look at it. They can tell from the watermarks, paper stock and also look up the check in their records

If the issuing bank does not have a branch in your town, call that bank on the number on their website, tell them that you got a cashier's check that you think could possibly be fake, and ask them if they can look up the check number. They will ask you for the date and amount of the check and can compare it to what they have on file to see if the details match up or not

contact the issuing bank and talk to them

You attempt to cash it, don't send the product till the bank tells you it with through WITHOUT coming back as fake. This may take up to 3 weeks. Ask your bank how long it would be before they know for sure.

One simple test. Google the routing number and see if it matches the bank.

However, if the scammer was smart and put the correct routing number on the check, then there is no way to tell.

My scammers are smart enough to use the correct routing number and the check only bounces because the account number does not exist at that bank.

all you can do is present it to your bank and let them process it, if it is no good it will be back in less than two weeks, so don't spend the money until the funds are there