Paper never refused ink. Websites never refused hype. If you can't deliver within twenty-four hours, then don't promise to. Be simple, clear and precise. Time is the scarcest resource, so never use five sentences when one will do.
People are confused enough today.
State your offer clearly. Tell them quickly if they're not a customer you can supply. There's nothing I find more frustrating than finding out at the last moment that they can't deliver to Ireland. There has never been an article that cannot be made shorter. Give them detail.