diff --git a/TODO.md b/TODO.md
index a727030..e87f8ea 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,4 +1,3 @@
-- [ ] Check config relations between runner and notification groups on start
 - [ ] Add option to send "incident resolved" notifications
 - [ ] Add Matrix notificator
 - [ ] Add Telegram notificator
diff --git a/config.go b/config.go
index 041bb77..c7cb409 100644
--- a/config.go
+++ b/config.go
@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"os"
+	"strings"
 	"time"
 
 	"gopkg.in/yaml.v3"
@@ -54,15 +55,48 @@ func ReadConfig(file string) (*Config, error) {
 	if err != nil {
 		return nil, fmt.Errorf("config: %w", err)
 	}
+	return parseConfig(data)
+}
+
+func parseConfig(data []byte) (*Config, error) {
 	c := new(Config)
-	err = yaml.Unmarshal(data, c)
-	if err != nil {
+	if err := yaml.Unmarshal(data, c); err != nil {
 		return nil, fmt.Errorf("config: %w", err)
 	}
 	return c, validateConfig(c)
 }
 
-func validateConfig(_ *Config) error {
-	// todo(alexvanin): set defaults and validate values such as bad email addresses
+func validateConfig(cfg *Config) error {
+	// Step 1: sanity check of notification groups
+	configuredNotifications := make(map[string]map[string]struct{})
+	if cfg.Notifications.Email != nil {
+		emailMap := make(map[string]struct{}, len(cfg.Notifications.Email.Groups))
+		for _, group := range cfg.Notifications.Email.Groups {
+			if len(group.Addresses) == 0 {
+				return fmt.Errorf("email group %s contains no addresses", group.Name)
+			}
+			if _, ok := emailMap[group.Name]; ok {
+				return fmt.Errorf("non unique email group name %s", group.Name)
+			}
+			emailMap[group.Name] = struct{}{}
+		}
+		configuredNotifications["email"] = emailMap
+	}
+	// With new notification channels, add more sanity checks
+
+	// Step 2: sanity check of command notifications
+	for _, cmd := range cfg.Commands {
+		for _, n := range cmd.Notifications {
+			elements := strings.Split(n, ":")
+			if len(elements) != 2 {
+				return fmt.Errorf("invalid notification tuple %s in command %s", n, cmd.Name)
+			} else if groups, ok := configuredNotifications[elements[0]]; !ok {
+				return fmt.Errorf("invalid notification type %s in command %s", elements[0], cmd.Name)
+			} else if _, ok = groups[elements[1]]; !ok {
+				return fmt.Errorf("invalid notification group %s in command %s", elements[1], cmd.Name)
+			}
+		}
+	}
+
 	return nil
 }
diff --git a/config_test.go b/config_test.go
new file mode 100644
index 0000000..7b5ffb0
--- /dev/null
+++ b/config_test.go
@@ -0,0 +1,102 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+var testCases = [...]struct {
+	config  string
+	isValid bool
+	errMsg  string
+}{
+	{
+		config: `
+state:
+  bolt: ./nz.state
+notifications:
+  email:
+    smtp: smtp.gmail.com:587
+    login: nzbx@corp.com
+    password: secret
+    groups:
+      - name: developers
+        addresses:
+          - alex@corp.com
+commands:
+  - name: Test command
+    exec: ./script.sh arg1
+    cron: "*/5 * * * *"
+    interval: 10s
+    timeout: 2s
+    threshold: 3
+    threshold_sleep: 5s
+    notifications:
+      - email:developers`,
+		isValid: true,
+	},
+	{
+		config: `
+notifications:
+  email:
+    groups:
+      - name: developers`,
+		errMsg: "contains no addresses",
+	},
+	{
+		config: `
+notifications:
+  email:
+    groups:
+      - name: developers
+        addresses:
+          - foo@corp.com
+      - name: developers
+        addresses:
+          - bar@corp.com
+`,
+		errMsg: "non unique email group name",
+	},
+	{
+		config: `
+commands:
+  - name: Test command
+    notifications:
+      - hello wolrd`,
+		errMsg: "invalid notification tuple",
+	},
+	{
+		config: `
+commands:
+  - name: Test command
+    notifications:
+      - foo:bar`,
+		errMsg: "invalid notification type",
+	},
+	{
+		config: `
+notifications:
+  email:
+    groups:
+      - name: developers
+        addresses:
+          - foo@corp.com
+commands:
+  - name: Test command
+    notifications:
+      - email:ops`,
+		errMsg: "invalid notification group",
+	},
+}
+
+func TestParseConfig(t *testing.T) {
+	for i, testCase := range testCases {
+		_, err := parseConfig([]byte(testCase.config))
+		require.Equal(t, testCase.isValid, err == nil, fmt.Sprintf("test:%d, err:%s", i, err))
+		if !testCase.isValid {
+			require.Contains(t, err.Error(), testCase.errMsg)
+		}
+	}
+}
diff --git a/go.mod b/go.mod
index 96556bc..7bdcf99 100644
--- a/go.mod
+++ b/go.mod
@@ -5,12 +5,15 @@ go 1.18
 require (
 	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510
 	github.com/robfig/cron/v3 v3.0.0
+	github.com/stretchr/testify v1.7.0
 	go.etcd.io/bbolt v1.3.6
 	go.uber.org/zap v1.21.0
 	gopkg.in/yaml.v3 v3.0.0-20220512140231-539c8e751b99
 )
 
 require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	go.uber.org/atomic v1.9.0 // indirect
 	go.uber.org/multierr v1.8.0 // indirect
 	golang.org/x/sys v0.0.0-20210510120138-977fb7262007 // indirect