Let's Encrypt announced today that from January 2018 free wildcard certificates be issued.
Wildcard certificates (e.g. *.frankysweb.de) allow you to secure an entire domain via SSL with one certificate. With other certification authorities, wildcard certificates cost quite a bit of money, the cheapest wildcard certificate I know so far is just under 280 EUR for a 3-year term.
Wildcard certificates are not only often used for Exchange servers, wildcard certificates are also commonly used for load balancers and web application firewalls.
Let's Encrypt currently offers the only free certificates that are also considered trustworthy by all common devices. So far, however, Let's Encrypt has only issued single domain and SAN certificates. The duration of the certificates is 3 months, but the renewal of the certificates can be completely automated.
From January 2018, Let's Encrypt will also issue free wildcard certificates, probably again with a 3-month term. The domain will be validated via DNS and a client. In January, the ACME v2 API which will then also support wildcard certificates.
