diff --git a/pymodmilter/base.py b/pymodmilter/base.py
index aa5cea8..eb1363d 100644
--- a/pymodmilter/base.py
+++ b/pymodmilter/base.py
@@ -16,7 +16,8 @@ __all__ = [
     "CustomLogger",
     "BaseConfig",
     "MilterMessage",
-    "replace_illegal_chars"]
+    "replace_illegal_chars",
+    "config_schema"]
 
 import logging
 
@@ -134,3 +135,462 @@ class MilterMessage(MIMEPart):
 def replace_illegal_chars(string):
     """Remove illegal characters from header values."""
     return "".join(string.replace("\x00", "").splitlines())
+
+
+JSON_CONFIG_SCHEMA = """
+{
+    "$id": "https://example.com/schemas/config",
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "title": "Root",
+    "type": "object",
+    "required": ["rules"],
+    "additionalProperties": false,
+    "properties": {
+        "global": {
+            "title": "Section global",
+            "type": "object",
+            "additionalProperties": false,
+            "properties": {
+                "local_addrs": { "$ref": "/schemas/config/hosts" },
+                "loglevel":    { "$ref": "/schemas/config/loglevel" },
+                "socket": {
+                    "title": "Socket",
+                    "type": "string",
+                    "pattern": "^((unix|local):.+|inet6?:[0-9]{1,5}(@.+)?)$"
+                }
+            }
+        },
+        "rules": {
+            "title": "Section rules",
+            "type": "array",
+            "items": {
+                "title": "Rules",
+                "type": "object",
+                "required": [
+                    "actions"
+                ],
+                "additionalProperties": false,
+                "properties": {
+                    "name":       { "$ref": "/schemas/config/name" },
+                    "pretend":    { "$ref": "/schemas/config/pretend" },
+                    "conditions": { "$ref": "/schemas/config/conditions" },
+                    "loglevel":   { "$ref": "/schemas/config/loglevel" },
+                    "actions": {
+                        "title": "Section actions",
+                        "type": "array",
+                        "items": {
+                            "title": "Actions",
+                            "type": "object",
+                            "required": ["type"],
+                            "properties": {
+                                "type": { "$ref": "/schemas/config/actiontype" }
+                            },
+                            "if": { "properties": { "type": { "const": "add_header" } } },
+                            "then": { "$ref": "/schemas/config/add_header" },
+                            "else": {
+                                "if": { "properties": { "type": { "const": "mod_header" } } },
+                                "then": { "$ref": "/schemas/config/mod_header" },
+                                "else": {
+                                    "if": { "properties": { "type": { "const": "del_header" } } },
+                                    "then": { "$ref": "/schemas/config/del_header" },
+                                    "else": {
+                                        "if": { "properties": { "type": { "const": "add_disclaimer" } } },
+                                        "then": { "$ref": "/schemas/config/add_disclaimer" },
+                                        "else": {
+                                            "if": { "properties": { "type": { "const": "rewrite_links" } } },
+                                            "then": { "$ref": "/schemas/config/rewrite_links" },
+                                            "else": {
+                                                "if": { "properties": { "type": { "const": "store" } } },
+                                                "then": { "$ref": "/schemas/config/store" },
+                                                "else": {
+                                                    "if": { "properties": { "type": { "const": "notify" } } },
+                                                    "then": { "$ref": "/schemas/config/notify" },
+                                                    "else": {
+                                                        "if": { "properties": { "type": { "const": "quarantine" } } },
+                                                        "then": { "$ref": "/schemas/config/quarantine" },
+                                                        "else": {
+                                                            "additionalProperties": false
+                                                        }
+                                                    }
+                                                }
+                                            }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    },
+    "$defs": {
+        "name": {
+            "$id": "/schemas/config/name",
+            "title": "Name",
+            "type": "string",
+            "pattern": "^.+$"
+        },
+        "hosts": {
+            "$id": "/schemas/config/hosts",
+            "title": "Hosts/networks",
+            "type": "array",
+            "items": {
+                "title": "Hosts/Networks",
+                "type": "string",
+                "pattern": "^.+$"
+            }
+        },
+        "pretend": {
+            "$id": "/schemas/config/pretend",
+            "title": "Pretend",
+            "type": "boolean"
+        },
+        "loglevel": {
+            "$id": "/schemas/config/loglevel",
+            "title": "Loglevel",
+            "type": "string",
+            "pattern": "^(critical|error|warning|info|debug)$"
+        },
+        "actiontype": {
+            "$id": "/schemas/config/actiontype",
+            "title": "Action type",
+            "enum": [
+                "add_header", "mod_header", "del_header", "add_disclaimer",
+                "rewrite_links", "store", "notify", "quarantine"]
+        },
+        "storagetype": {
+            "$id": "/schemas/config/storagetype",
+            "title": "Storage type",
+            "enum": ["file"]
+        },
+        "whitelisttype": {
+            "$id": "/schemas/config/whitelisttype",
+            "title": "Whitelist type",
+            "enum": ["db"]
+        },
+        "field": {
+            "$id": "/schemas/config/field",
+            "title": "Field",
+            "type": "string",
+            "pattern": "^.+$"
+        },
+        "value": {
+            "$id": "/schemas/config/value",
+            "title": "Value",
+            "type": "string",
+            "pattern": "^.+$"
+        },
+        "original": {
+            "$id": "/schemas/config/original",
+            "title": "Original",
+            "type": "boolean"
+        },
+        "metavar": {
+            "$id": "/schemas/config/metavar",
+            "title": "Meta variable",
+            "type": "string",
+            "pattern": "^.+$"
+        },
+        "conditions": {
+            "$id": "/schemas/config/conditions",
+            "title": "Conditions",
+            "type": "object",
+            "properties": {
+                "metavar": { "$ref": "/schemas/config/metavar" },
+                "local": {
+                    "title": "Local",
+                    "type": "boolean"
+                },
+                "hosts": {
+                    "title": "Hosts/Networks",
+                    "type": "array",
+                    "items":{
+                        "title": "Host/Network",
+                        "type": "string",
+                        "pattern": "^.+$"
+                    }
+                },
+                "envfrom": {
+                    "title": "Envelope from",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "envto": {
+                    "title": "Envelope to",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "header": {
+                    "title": "Header",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "var": {
+                    "title": "Variable",
+                    "type": "string",
+                    "pattern": "^.+$"
+                }
+            },
+            "additionalProperties": false,
+            "anyOf": [
+                {"required": ["local"]},
+                {"required": ["hosts"]},
+                {"required": ["envfrom"]},
+                {"required": ["envto"]},
+                {"required": ["header"]},
+                {"required": ["var"]}
+            ]
+        },
+        "add_header": {
+            "$id": "/schemas/config/add_header",
+            "title": "Add header",
+            "type": "object",
+            "required": ["type", "field", "value"],
+            "properties": {
+                "type":       { "$ref": "/schemas/config/actiontype" },
+                "name":       { "$ref": "/schemas/config/name" },
+                "pretend":    { "$ref": "/schemas/config/pretend" },
+                "conditions": { "$ref": "/schemas/config/conditions" },
+                "loglevel":   { "$ref": "/schemas/config/loglevel" },
+                "field":      { "$ref": "/schemas/config/field" },
+                "value":      { "$ref": "/schemas/config/value" }
+            },
+            "additionalProperties": false
+        },
+        "mod_header": {
+            "$id": "/schemas/config/mod_header",
+            "title": "Modify header",
+            "type": "object",
+            "required": ["type", "field", "value"],
+            "properties": {
+                "type":       { "$ref": "/schemas/config/actiontype" },
+                "name":       { "$ref": "/schemas/config/name" },
+                "pretend":    { "$ref": "/schemas/config/pretend" },
+                "conditions": { "$ref": "/schemas/config/conditions" },
+                "loglevel":   { "$ref": "/schemas/config/loglevel" },
+                "field":      { "$ref": "/schemas/config/field" },
+                "value":      { "$ref": "/schemas/config/value" },
+                "search": {
+                    "title": "Search",
+                    "type": "string",
+                    "pattern": "^.+$"
+                }
+            },
+            "additionalProperties": false
+        },
+        "del_header": {
+            "$id": "/schemas/config/del_header",
+            "title": "Delete header",
+            "type": "object",
+            "required": ["type", "field"],
+            "properties": {
+                "type":       { "$ref": "/schemas/config/actiontype" },
+                "name":       { "$ref": "/schemas/config/name" },
+                "pretend":    { "$ref": "/schemas/config/pretend" },
+                "conditions": { "$ref": "/schemas/config/conditions" },
+                "loglevel":   { "$ref": "/schemas/config/loglevel" },
+                "field":      { "$ref": "/schemas/config/field" },
+                "value":      { "$ref": "/schemas/config/value" }
+            },
+            "additionalProperties": false
+        },
+        "add_disclaimer": {
+            "$id": "/schemas/config/add_disclaimer",
+            "title": "Add disclaimer",
+            "type": "object",
+            "required": ["type", "action", "html_template", "text_template"],
+            "properties": {
+                "type":       { "$ref": "/schemas/config/actiontype" },
+                "name":       { "$ref": "/schemas/config/name" },
+                "pretend":    { "$ref": "/schemas/config/pretend" },
+                "conditions": { "$ref": "/schemas/config/conditions" },
+                "loglevel":   { "$ref": "/schemas/config/loglevel" },
+                "action": {
+                    "title": "Action",
+                    "enum": ["append", "prepend"]
+                },
+                "html_template": {
+                    "title": "HTML template",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "text_template": {
+                    "title": "Text template",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "error_policy": {
+                    "title": "Action",
+                    "enum": [
+                        "wrap", "ignore", "reject",
+                        "WRAP", "IGNORE", "REJECT"]
+                }
+            },
+            "additionalProperties": false
+        },
+        "rewrite_links": {
+            "$id": "/schemas/config/rewrite_links",
+            "title": "Rewrite links",
+            "type": "object",
+            "required": ["type", "repl"],
+            "properties": {
+                "type":       { "$ref": "/schemas/config/actiontype" },
+                "name":       { "$ref": "/schemas/config/name" },
+                "pretend":    { "$ref": "/schemas/config/pretend" },
+                "conditions": { "$ref": "/schemas/config/conditions" },
+                "loglevel":   { "$ref": "/schemas/config/loglevel" },
+                "repl": {
+                    "title": "Replacement",
+                    "type": "string",
+                    "pattern": "^.+$"
+                }
+            },
+            "additionalProperties": false
+        },
+        "store": {
+            "$id": "/schemas/config/store",
+            "title": "Store",
+            "type": "object",
+            "required": ["storage_type"],
+            "properties": {
+                "storage_type": { "$ref": "/schemas/config/storagetype" }
+            },
+            "if": { "properties": { "storage_type": { "const": "file" } } },
+            "then": {
+                "properties": {
+                    "type":       { "$ref": "/schemas/config/actiontype" },
+                    "storage_type": { "$ref": "/schemas/config/storagetype" },
+                    "name":       { "$ref": "/schemas/config/name" },
+                    "pretend":    { "$ref": "/schemas/config/pretend" },
+                    "conditions": { "$ref": "/schemas/config/conditions" },
+                    "loglevel":   { "$ref": "/schemas/config/loglevel" },
+                    "original":   { "$ref": "/schemas/config/original" },
+                    "metavar":    { "$ref": "/schemas/config/metavar" },
+                    "directory": {
+                        "title": "Directory",
+                        "type": "string",
+                        "pattern": "^.+$"
+                    }
+                },
+                "additionalProperties": false
+            },
+            "else": {
+                "additionalProperties": false
+            }
+        },
+        "notify": {
+            "$id": "/schemas/config/notify",
+            "title": "Notify",
+            "type": "object",
+            "required": ["smtp_host", "smtp_port", "envelope_from", "from_header", "subject", "template"],
+            "properties": {
+                "type":       { "$ref": "/schemas/config/actiontype" },
+                "name":       { "$ref": "/schemas/config/name" },
+                "pretend":    { "$ref": "/schemas/config/pretend" },
+                "conditions": { "$ref": "/schemas/config/conditions" },
+                "loglevel":   { "$ref": "/schemas/config/loglevel" },
+                "smtp_host": {
+                    "title": "SMTP host",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "smtp_port":  {
+                    "title": "SMTP port",
+                    "type": "number"
+                },
+                "envelope_from":  {
+                    "title": "Envelope from",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "from_header":  {
+                    "title": "From-Header",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "subject":  {
+                    "title": "Subject",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "template":  {
+                    "title": "Template",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "repl_img":  {
+                    "title": "Replacement image",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "embed_imgs": {
+                    "title": "Embedded images",
+                    "type": "array",
+                    "items": {
+                        "title": "Embedded image",
+                        "type": "string",
+                        "pattern": "^.+$"
+                    }
+                }
+            },
+            "additionalProperties": false
+        },
+        "quarantine": {
+            "$id": "/schemas/config/quarantine",
+            "title": "Quarantine",
+            "type": "object",
+            "required": ["storage"],
+            "properties": {
+                "type":         { "$ref": "/schemas/config/actiontype" },
+                "name":         { "$ref": "/schemas/config/name" },
+                "pretend":      { "$ref": "/schemas/config/pretend" },
+                "conditions":   { "$ref": "/schemas/config/conditions" },
+                "loglevel":     { "$ref": "/schemas/config/loglevel" },
+                "storage":      { "$ref": "/schemas/config/store" },
+                "notification": { "$ref": "/schemas/config/notify" },
+                "milter_action": {
+                    "title": "Milter action",
+                    "enum": [
+                        "reject", "discard", "accept",
+                        "REJECT", "DISCARD", "ACCEPT"]
+                },
+                "reject_reason": {
+                    "title": "Reject reason",
+                    "type": "string",
+                    "pattern": "^.+$"
+                },
+                "whitelist": {
+                    "title": "Whitelist",
+                    "type": "object",
+                    "required": ["type"],
+                    "properties": {
+                        "type": { "$ref": "/schemas/config/whitelisttype" }
+                    },
+                    "if": { "properties": { "type": { "const": "db" } } },
+                    "then": {
+                        "required": ["connection", "table"],
+                        "properties": {
+                            "type": { "$ref": "/schemas/config/whitelisttype" },
+                            "connection": {
+                                "title": "DB connection",
+                                "type": "string",
+                                "pattern": "^.+$"
+                            },
+                            "table": {
+                                "title": "DB table",
+                                "type": "string",
+                                "pattern": "^.+$"
+                            }
+                        },
+                        "additionalProperties": false
+                    },
+                    "else": {
+                        "additionalProperties": false
+                    }
+                }
+            }
+        }
+    }
+}
+"""