honestly gmail is a very friendly mail destination. fix your spf/dkim/ptr records and they'll probably accept the mail.
all the shitty servers around are MUCH worse and handle spam way more brutally. Microsoft/Hotmail, most ISP mail servers, give generic error messages and block whole ranges by default, and getting something unblocked is a big fucking waste of time.
@CobaltVelvet my previous job was at an ISP, one of my projects involved changing the IP addresses of our relay servers. Google was pretty easy to deal with but Yahoo was almost impossible. The worst thing was they'd keep saying that they whitelisted us but the next day we'd get blocked again. It was only because our parent company had a relationship with them that we managed to get it sorted in the end. Email is hard!
