The rate limits, and which ones can be increased upon request, are pretty clearly posted on their web site: letsencrypt.org Rate Limits Let’s Encrypt provides rate limits to ensure fair usage by as many people as possible. We believe these rate limits are high enough to work for most people by default. We’ve also designed them so that renewing a certificate almost never hits a rate... There isn't any kind of "sales team" to talk with (since there's nothing for sale), but if you have specific questions and post them here it may be that someone on this community forum could help point you to the answers.