Let's understand how a proxy server works and the criteria for choosing a provider

For white email campaigns through MailChimp or SendGrid, static will work. For gray promotion, better take dynamics and change IP every 300-500 emails. Otherwise you'll quickly fly into spam lists of all mail providers.

It's when the proxy server automatically changes your IP address. You connect once, and then the system switches addresses from its pool. How often to change - you configure yourself.

Much more expensive. Static IP costs $50-200 per month. For this money you can buy 25-100 GB of traffic on dynamic proxies. That's thousands of different IPs instead of one.

Of course you can. Many do exactly that. Static for admin panels and important accounts, dynamic for tests and mass operations. But ideally, it's better to use residential proxies with configurable rotation. They combine advantages of both types. For important accounts, set sticky session for 72 hours and get almost static IP. For scraping, enable fast rotation every 5 minutes. All in one service, with one balance, without needing to buy different proxy types. Plus all IPs look like real users, which is critically important for modern platforms.

Elementary check. Go to 2ip.ru or whoer.net several times during the day. If the IP doesn't change, the proxy is static. You can also ping the target server through command line and watch the route. It should also be constant.