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.
@Madeorsk i can't remember the last time i received a .zip by mail that wasn't malware
tbh mail is just awful with files. it feels and works like it was improvised on top of another protocol.
@Madeorsk just sent myself a zip on gmail, worked fine
@CobaltVelvet I know but my teachers needed to receive a zip file of my project and never received it. I don't like this "protection" as it can be easily bypassed with a .rar file (or things in docx files for example) and is problematic when you just want to send a non-malware file to someone.
Also, that's the best way to send a file to someone without having time restrictions or websites full of crap, like wetransfer that everyone use (as long as it's not 4GB files obviously).