diff --git a/Readme.md b/Readme.md
index 2fe6008..642a31a 100644
--- a/Readme.md
+++ b/Readme.md
@@ -60,6 +60,14 @@ This fixes the causes of lint warnings (where possible).
 - MAIL_SERVER_BLACKLIST
   - list of domains, separated by comma
   - if the user tries to use such a mail service, then he will get the notification that this provider is not supported
+- MAIL_WHITELIST
+  - list of mail addresses (``someone@somewhere.com``) or domains (``mailbox.org``), separated by comma
+  - if a user requests signing in with a mail address which is not in this list, then the request is rejected
+  - if the list is empty, then any mail address (except with domains from the blacklist) is allowed
+  - note: this allows a third party who knows the server url to check if a certain mail address is allowed by trying to sign in with it
+- DISABLE_SIGNUP
+  - ``yes`` or ``no`` (default: no)
+  - disables creating new families if ``yes`` is selected
 
 ## HTTPS
 
diff --git a/src/api/auth.ts b/src/api/auth.ts
index fb4b588..985c598 100644
--- a/src/api/auth.ts
+++ b/src/api/auth.ts
@@ -1,6 +1,6 @@
 /*
  * server component for the TimeLimit App
- * Copyright (C) 2019 Jonas Lochmann
+ * Copyright (C) 2019 - 2020 Jonas Lochmann
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
@@ -20,7 +20,7 @@ import { Router } from 'express'
 import { BadRequest } from 'http-errors'
 import { Database } from '../database'
 import { sendLoginCode, signInByMailCode } from '../function/authentication/login-by-mail'
-import { isMailServerBlacklisted, sanitizeMailAddress } from '../util/mail'
+import { isMailAddressCoveredByWhitelist, isMailServerBlacklisted, sanitizeMailAddress } from '../util/mail'
 import {
   isSendMailLoginCodeRequest,
   isSignInByMailCodeRequest
@@ -41,7 +41,9 @@ export const createAuthRouter = (database: Database) => {
         throw new BadRequest()
       }
 
-      if (isMailServerBlacklisted(mail)) {
+      if (!isMailAddressCoveredByWhitelist(mail)) {
+        res.json({ mailAddressNotWhitelisted: true })
+      } else if (isMailServerBlacklisted(mail)) {
         res.json({ mailServerBlacklisted: true })
       } else {
         const { mailLoginToken } = await sendLoginCode({
diff --git a/src/api/parent.ts b/src/api/parent.ts
index ef534cd..04ea3aa 100644
--- a/src/api/parent.ts
+++ b/src/api/parent.ts
@@ -1,6 +1,6 @@
 /*
  * server component for the TimeLimit App
- * Copyright (C) 2019 Jonas Lochmann
+ * Copyright (C) 2019 - 2020 Jonas Lochmann
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
@@ -17,7 +17,8 @@
 
 import { json } from 'body-parser'
 import { Router } from 'express'
-import { BadRequest, Unauthorized } from 'http-errors'
+import { BadRequest, Forbidden, Unauthorized } from 'http-errors'
+import { config } from '../config'
 import { Database } from '../database'
 import { removeDevice } from '../function/device/remove-device'
 import { canRecoverPassword } from '../function/parent/can-recover-password'
@@ -47,7 +48,11 @@ export const createParentRouter = ({ database, websocket }: {database: Database,
       const { mailAuthToken } = req.body
       const { status, mail } = await getStatusByMailToken({ database, mailAuthToken })
 
-      res.json({ status, mail })
+      res.json({
+        status,
+        mail,
+        canCreateFamily: !config.disableSignup
+      })
     } catch (ex) {
       next(ex)
     }
@@ -55,6 +60,10 @@ export const createParentRouter = ({ database, websocket }: {database: Database,
 
   router.post('/create-family', json(), async (req, res, next) => {
     try {
+      if (config.disableSignup) {
+        throw new Forbidden()
+      }
+
       if (!isCreateFamilyByMailTokenRequest(req.body)) {
         throw new BadRequest()
       }
diff --git a/src/config.ts b/src/config.ts
new file mode 100644
index 0000000..508c89f
--- /dev/null
+++ b/src/config.ts
@@ -0,0 +1,37 @@
+/*
+ * server component for the TimeLimit App
+ * Copyright (C) 2019 - 2020 Jonas Lochmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+// note: soem configuration parameters are read directly at the location where they are used
+interface Config {
+  mailWhitelist: Array<string>
+  disableSignup: boolean
+}
+
+function parseYesNo (value: string) {
+  if (value === 'yes') {
+    return true
+  } else if (value === 'no') {
+    return false
+  } else {
+    throw new Error('invalid value "' + value + '", expected "" or "no"')
+  }
+}
+
+export const config: Config = {
+  mailWhitelist: (process.env.MAIL_WHITELIST || '').split(',').map((item) => item.trim()).filter((item) => item.length > 0),
+  disableSignup: parseYesNo(process.env.DISABLE_SIGNUP || 'no')
+}
diff --git a/src/util/mail.ts b/src/util/mail.ts
index 9a32002..989ef75 100644
--- a/src/util/mail.ts
+++ b/src/util/mail.ts
@@ -18,6 +18,7 @@
 import { parseOneAddress } from 'email-addresses'
 import * as Email from 'email-templates'
 import { join } from 'path'
+import { config } from '../config'
 
 const mailimprint = process.env.MAIL_IMPRINT || 'not defined'
 const mailServerBlacklist = (process.env.MAIL_SERVER_BLACKLIST || '').split(',').filter((item) => !!item)
@@ -84,13 +85,40 @@ export const sendUninstallWarningMail = async ({ receiver, deviceName }: {
   })
 }
 
-export function isMailServerBlacklisted (mail: string) {
+export function isMailServerBlacklisted (mail: string): boolean {
   const parts = mail.split('@')
   const domain = parts[parts.length - 1]
 
   return mailServerBlacklist.indexOf(domain.toLowerCase()) !== -1
 }
 
+export function isMailAddressCoveredByWhitelist (mail: string): boolean {
+  if (config.mailWhitelist.length === 0) {
+    return true
+  }
+
+  const mailParts = mail.split('@')
+  const mailDomain = mailParts[mailParts.length - 1]
+
+  for (let i = 0; i < config.mailWhitelist.length; i++) {
+    const whtielistItem = config.mailWhitelist[i]
+
+    const isDomain = whtielistItem.indexOf('@') === -1
+
+    if (isDomain) {
+      if (mailDomain === whtielistItem) {
+        return true
+      }
+    } else {
+      if (mail === whtielistItem) {
+        return true
+      }
+    }
+  }
+
+  return false
+}
+
 export function sanitizeMailAddress (input: string): string | null {
   const parsed = parseOneAddress(input)