Since 17:09 UTC there are two new monitor types, both made for hosting companies and anyone who runs mail.
Blacklist (DNSBL) checks a domain's addresses and those of its mail servers, or a single IPv4 address, against SpamCop and Barracuda, and turns down while any of them is listed, naming the address and the list. You hear about it before your customers' mail starts bouncing.
Email authentication checks that a domain has one SPF record, a DMARC record with a valid policy, and a DKIM key for each selector you name. It also warns when SPF needs more than 10 DNS lookups.
Both are DNS lookups made by our central server, so they use no probes and no credits. They run every hour by default, every 15 minutes at the fastest.
And the Cloud provider status form now has a Provider list: pick GitHub, Cloudflare, Shopify, OpenAI or any of 35 providers, and the address and name are filled in. Details in Monitor types.