If you try to post a message and get an error such as this...
the easiest way to solve it is to run a VPN. There are 'free' VPN's but a paid for one such as NordVPN is probably a better idea. Personally, I always run a VPN if I'm surfing the net on a public wifi, such as in a hotel. I use it when accessing on-line banking too.
As I understand it (but I'm sure someone more geeky than me can add knowledge...) it means that someone at some time in the past has sent Spam out from an IP address in this range, so they are now blocked. IT IS NOT ME BLOCKING YOU! I have had a couple of people send snotty emails complaining that I'd blocked them. Oddly, neither replied when I explained how to get around it and didn't offer an apology for their belligerent tone, but hey-ho
I ***THINK*** you ***SHOULD*** be able to switch your router off & one again, (leave it off over night if you can) and you'll get a new IP address. But when I get the message, as I did above, I just hit the VPN.