Also, any warrant asking to just search the entire house should be rejected, too.
I'm no police apologist, but what you're saying is downright silly.
If the police have enough evidence that shows you own a firearm of the same caliber as the murder weapon, and some other evidence indicates you might be guilty (e.g., motive), then they shouldn't need to know what room in your house you keep your gun in order to get a search warrant.
In this case, if the police have enough other evidence that you have evidence of your money laundering in your GMail account, I don't see it unreasonable that they can search all the e-mail. It really isn't any different from getting a warrant to search the entire contents of a specific filing cabinet in your home, and it really is an unreasonable burden to require the police to also know the color of the paper the evidence is printed on, as well as which file folder contains the paper.