> Let's Encrypt applies per-domain name rate limits and these domain names see lots of issuance requests. There's a process to lift those limits.

I'm familiar with the process to lift those limits, and Let's Encrypt has been amenable to bumping the certs as high as 250,000 but balked at 500,000, saying, "This is too large for us to support"

(I run a DNS service nip.io / sslip.io, and lots of my users request certs, so I'm always bumping into the limits)