diff --git a/README.md b/README.md
index 347f884..0c3fedf 100644
--- a/README.md
+++ b/README.md
@@ -65,7 +65,7 @@ By default the directory (work_dir) containing the working data (csr,certificate
 | --revoke-reason         | **c**             | Provide a reason code for the revocation (see https://tools.ietf.org/html/rfc5280#section-5.3.1 for valid values)                            |                                      |
 | domain (san-domain...): | **d**             | (domainconfig section start) Domains to use in the cert request. This value will be MD5-hashed as cert_id.                                   |                                      |
 | api                     | d,**g**           | Determines the API version used                                                                                                              | v2                                   |
-| authority               | d,**g**           | URL to the certificate authorities API                                                                                                       | https://acme-v02.api.letsencrypt.org |
+| authority               | d,**g**           | URL to the certificate authorities ACME API root (without trailing /directory or similar)                                                    | https://acme-v02.api.letsencrypt.org |
 | authority_tos_agreement | d,**g**,c         | Indicates agreement to the ToS of the certificate authority (--authority-tos-agreement on command line)                                      |                                      |
 | authority_contact_email | d,**g**           | (v2 API only) Contact e-mail to be registered with your account key                                                                          |                                      |
 | account_key             | d,**g**           | Path to the account key                                                                                                                      | {work_dir}/account.key               |
diff --git a/docs/domain.yaml b/docs/domain.yaml
index 801d5a8..6c7e442 100644
--- a/docs/domain.yaml
+++ b/docs/domain.yaml
@@ -68,3 +68,12 @@ mail.example.com smtp.example.com webmail.example.net *.intra.example.com:
   perm: '400'
   format: crt,ca
   action: '/etc/init.d/postfix reload'
+
+# this will use a different authority for the following set of domains (buypass.com in this example)
+buypass-example.com *.buypass-example.com:
+- authority: 'https://api.buypass.com/acme'  # Removed trailing /directory from buypass docs for API endpoint
+  mode: dns.nsupdate
+  nsupdate_keyname: buypass
+  nsupdate_keyvalue: Test1234512359==
+  nsupdate_keyalgorithm: HMAC-MD5.SIG-ALG.REG.INT
+