@selea I like how this is literally the email version of judging people by the colour of their skin.
Again, this is not a technical problem. I've attached the message I got from gmail below. They tell me they've received "an unusual rate of unsolicited mail originating from your SPF domain". They're lying. I checked my outgoing mail logs, this was the first email sent to gmail in over 2 weeks. And anything trying to send in my name but not going through my mail server should surely fail due to SPF and DKIM.
This is not a technical problem, it's a corporate politics problem where Gmail doesn't like any party that isn't paying them. There's hundreds of thousands of cases of this on the net, and the one "solution" that works for people is paying some big email provider.