Gmail is blocking email from my IP

I’ve had a virtual private server for close to 6 months, and I’m going to start sending emails to users from noreply@mydomain.com.

I’ve probably sent 10 emails to my gmail address as a test, and gmail bounces my emails with the message:

Our system has detected an unusual rate of 550-5.7.28 unsolicited mail originating from your IP address. To protect our 550-5.7.28 users from spam, mail sent from your IP address has been blocked. 550-5.7.28 Please visit 550-5.7.28 https://support.google.com/mail/?p=UnsolicitedIPError to review our 550 5.7.28 Bulk Email Senders Guidelines. g9si1490378qvq.7 – gsmtp (in reply to end of DATA command))

I’ve visited the link they provide above, which goes to a page entitled Prevent mail to Gmail users from being blocked or sent to spam, but it mostly talks about how to avoid messages being treated as spam, not how to get an IP address unblocked. What can I do to have gmail unblock my IP address?

TMI 1 Only my virtual private server is using this IP address, and my VPS has not been sending out emails in all the time I’ve had it (aoubt 6 months). I didn’t even have postfix installed until a month ago, which is when I started testing emails to Gmail and getting bounces. (I didn’t try again until today; it isn’t as if I’ve been repeatedly sending bounce-worthy emails.) So I should think my IP address would have been unblocked by now if waiting patiently were the key.

TMI 2
I realize that I could pay to have an email service send my emails, but I’m just a solitary guy who’s trying to serve users and not take on additional expenses.