1and1 response to query to allow LetsEncrypt Certs

[My1]

well the first part of the Email can be ignored since it's not about using their certs with other servers, the main point of the email is seen here:

@TomasHradcky

On the other hand, there is no option for domain names hosted with 1&1 to use an external SSL. However, if you wish, you can purchase your SSL Certificate here in 1&1.

So in other words, "buy our certs or forget HTTPS".