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.
@val i tried, they forwarded my to symantec i think who managed the particular blocklist, which never replied to my ticket