diff --git a/README.md b/README.md
index 391b167..7afb605 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,8 @@ A blog software written in Typescript, with an Express.js backend and a Vue3 fro
 * [5010](http://localhost:5010): dev client
 * [5020](http://localhost:5020): dev postgres
 * [5030](https://localhost:5030): login portal (fake OAuth)
+* [5040](https://localhost:5040): dev SMTP server (HTTP port)
+* [5041](https://localhost:5041): dev SMTP server (SMTP port)
 * [5100](http://localhost:5100): production app
 * [5120](http://localhost:5120): production postgres
 
diff --git a/client/src/App.vue b/client/src/App.vue
index 9110b82..39c0ada 100644
--- a/client/src/App.vue
+++ b/client/src/App.vue
@@ -52,7 +52,7 @@
         </div>
       </nav>
 
-      <RouterView :userPermissions="loggedInUserInfo?.permissions" />
+      <RouterView :userPermissions="loggedInUserInfo?.permissions ?? DEFAULT_ROLE" />
     </div>
     <footer class="page-footer">
       <div class="container">
@@ -118,6 +118,7 @@ import { saveIdToken } from "@client/util/storage.js";
 import { faGithub } from "@fortawesome/free-brands-svg-icons";
 import { faExternalLink } from "@fortawesome/free-solid-svg-icons";
 import type { AppSettingsDto, LoggedInUserInfo } from "@fumix/fu-blog-common";
+import { DEFAULT_ROLE } from "@fumix/fu-blog-common";
 import { onMounted, ref, watch } from "vue";
 import { useI18n } from "vue-i18n";
 import { useRoute, useRouter } from "vue-router";
diff --git a/client/src/i18n/de.json b/client/src/i18n/de.json
index fdf18a4..f5fbfb2 100644
--- a/client/src/i18n/de.json
+++ b/client/src/i18n/de.json
@@ -73,7 +73,7 @@
       "not-available": {
         "title": "Post nicht vorhanden",
         "message": "Der Post ist nicht verfügbar oder wurde gelöscht. Sie können mit dem Button zur Startseite zurück, oder nutzen sie die Suchfunktion um einen bestimmten Post zu finden."
-      } 
+      }
     }
   },
   "admin": {
@@ -105,7 +105,8 @@
         "email": "E-mail",
         "username": "Benutzername",
         "fullname": "Dein Name"
-      }
+      },
+      "username-requirements": "Der Benutzername muss zwischen {min} und {max} Zeichen lang sein (ist {length} Zeichen lang) und darf nur aus den Buchstaben a-z/A-Z, den Zahlen 0-9 und den Zeichen ._- bestehen."
     },
     "user_not_found": "Benutzer nicht gefunden."
   }
diff --git a/client/src/i18n/en.json b/client/src/i18n/en.json
index c9353d2..61729f5 100644
--- a/client/src/i18n/en.json
+++ b/client/src/i18n/en.json
@@ -101,8 +101,9 @@
         "email": "Email",
         "username": "Username",
         "fullname": "Your name"
-      }
+      },
+      "username-requirements": "The username must be between 3 and 32 characters long and can only consist of letters a-z/A-Z, digits 0-9 and characters ._-"
     },
     "user_not_found": "User not found."
   }
-}
\ No newline at end of file
+}
diff --git a/client/src/util/api-client.ts b/client/src/util/api-client.ts
index 408d3b3..adb2f79 100644
--- a/client/src/util/api-client.ts
+++ b/client/src/util/api-client.ts
@@ -142,7 +142,7 @@ export class PostEndpoints {
 
   static async findPosts(pageIndex: number, itemsPerPage = 12, search: string | undefined = undefined, operator: "and" | "or" = "and") {
     return callServer<void, JsonMimeType, { data: [PublicPost[], number | null] }>(
-      `/api/posts/page/${pageIndex}/count/${itemsPerPage}${search ? `/search/${encodeURIComponent(search)}/operator/${operator}` : ""}###`,
+      `/api/posts/page/${pageIndex}/count/${itemsPerPage}${search ? `/search/${encodeURIComponent(search)}/operator/${operator}` : ""}`,
       "GET",
       "application/json",
       null,
diff --git a/docker-compose.yml b/docker-compose.yml
index ff743d3..0ff7850 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,4 +1,5 @@
-version: '3'
+name: "fublog-development"
+
 services:
 
   postgres-dev:
@@ -13,3 +14,9 @@ services:
       POSTGRES_DB: "fublog"
     ports:
       - "5020:5432"
+
+  mailhog:
+    image: mailhog/mailhog:v1.0.1
+    ports:
+      - "5041:1025"  # SMTP port
+      - "5040:8025" # HTTP port
diff --git a/docker/compose/.env.template b/docker/compose/.env.template
index 16150b8..e52fa19 100644
--- a/docker/compose/.env.template
+++ b/docker/compose/.env.template
@@ -32,6 +32,18 @@ APP_MAIN_WEBSITE_URL=https://fumix.de
 # OAUTH_GITLAB_2_ISSUER=
 # …
 
+###
+### E-Mail settings
+###
+EMAIL_SMTP_HOST=
+EMAIL_SMTP_FROM=
+EMAIL_SMTP_USER=
+EMAIL_SMTP_PASSWORD=
+## Allowed values: "TLS" or "STARTTLS". If not set, defaults to "TLS".
+# EMAIL_SMTP_SECURITY=TLS
+## Custom SMTP port. If not explicitly set, the default port is 465. Except when `EMAIL_SMTP_SECURITY=STARTTLS` is set, then the default is 587.
+# EMAIL_SMTP_PORT=465
+
 ###
 ### As soon as the first user is registered in the blog, you can
 ### delete everything in this file after this line.
diff --git a/server/.env.template b/server/.env.template
index ac2edef..103f5ae 100644
--- a/server/.env.template
+++ b/server/.env.template
@@ -8,3 +8,9 @@
 # OAUTH_FAKE_CLIENT_ID=… # Custom client ID (default value is `ID`)
 # OAUTH_FAKE_CLIENT_SECRET=… # Custom client secret (default value is `secret`)
 # OAUTH_FAKE_ISSUER=localhost:42 # Custom domain (default value is `localhost:5030`)
+
+# For development the user and password can be omitted
+EMAIL_SMTP_HOST=localhost
+EMAIL_SMTP_FROM=fublog@localhost
+EMAIL_SMTP_SECURITY=STARTTLS
+EMAIL_SMTP_PORT=5041
diff --git a/server/src/routes/auth.ts b/server/src/routes/auth.ts
index fa3eb40..9c1b266 100644
--- a/server/src/routes/auth.ts
+++ b/server/src/routes/auth.ts
@@ -11,6 +11,7 @@ import {
   OAuthUserInfoDto,
   UserInfoOAuthToken,
 } from "@fumix/fu-blog-common";
+import { sendNotificationEmailAboutNewRegistration } from "../service/email-service.js";
 import express, { Request, Response, Router } from "express";
 import fetch from "node-fetch";
 import { BaseClient, Issuer, TokenSet } from "openid-client";
@@ -232,9 +233,10 @@ router.post("/userinfo/register", async (req, res, next) => {
                     oauthId: oauthUserId,
                     user,
                   };
-                  await mgr
-                    .insert(OAuthAccountEntity, [oauthAccount])
-                    .then((it) => logger.info("New OAuth account created: " + JSON.stringify(oauthAccount)));
+                  await mgr.insert(OAuthAccountEntity, [oauthAccount]).then((it) => {
+                    sendNotificationEmailAboutNewRegistration(oauthAccount.user.username);
+                    logger.info("New OAuth account created: " + JSON.stringify(oauthAccount));
+                  });
                 })
                 .then(async () => {
                   const result: OAuthUserInfoDto = {
diff --git a/server/src/routes/posts.ts b/server/src/routes/posts.ts
index a20b41c..bdbc7bf 100644
--- a/server/src/routes/posts.ts
+++ b/server/src/routes/posts.ts
@@ -6,7 +6,7 @@ import {
   NewPostRequestDto,
   PostRequestDto,
 } from "@fumix/fu-blog-common";
-import logger from "@server/logger.js";
+import logger from "../logger.js";
 import express, { NextFunction, Request, Response, Router } from "express";
 import { In } from "typeorm";
 import { AppDataSource } from "../data-source.js";
diff --git a/server/src/service/email-service.ts b/server/src/service/email-service.ts
new file mode 100644
index 0000000..e63ed34
--- /dev/null
+++ b/server/src/service/email-service.ts
@@ -0,0 +1,62 @@
+import console from "console";
+import { createTransport } from "nodemailer";
+import { AppDataSource } from "../data-source.js";
+import { UserEntity } from "../entity/User.entity.js";
+import logger from "../logger.js";
+import { ClientSettings, EmailSettings } from "../settings.js";
+
+export function sendNotificationEmailAboutNewRegistration(newUsername: string) {
+  if (!canSendEmail()) {
+    console.info("Could not send email notification about new user registration to admins. No SMTP server is configured in `.env` file.");
+    return;
+  }
+
+  AppDataSource.manager
+    .getRepository(UserEntity)
+    .createQueryBuilder("find all admins")
+    .where("roles @> :role", { role: ["ADMIN"] }) // https://www.postgresql.org/docs/16/functions-array.html#ARRAY-OPERATORS-TABLE
+    .getMany()
+    .then((users) => {
+      console.log("Found users", users);
+      return users.map((user) => user.email);
+    })
+    .catch((e) => {
+      console.error("Failed to get admins", e);
+      return [];
+    })
+    .then((adminEmails) => {
+      if (adminEmails.length <= 0) {
+        logger.warn(`There are no admins yet. No notification email is sent about new user '${newUsername}'.`);
+      } else {
+        logger.debug(`Sending notification email about registration of new user '${newUsername}' to ${adminEmails.join(", ")}`);
+
+        sendEmail(
+          adminEmails,
+          "New user registered",
+          `Hi admins,
+a new user '${encodeURIComponent(newUsername)}' registered at ${ClientSettings.BASE_URL} .
+Visit ${ClientSettings.BASE_URL}/administration in order to give them some permissions.
+
+Kind regards,
+Your fuBlog`,
+        );
+      }
+    });
+}
+
+function canSendEmail(): boolean {
+  return !!(EmailSettings.SMTP_HOST && EmailSettings.SMTP_PORT && EmailSettings.SMTP_FROM);
+}
+
+function sendEmail(to: string[], subject: string, text: string) {
+  createTransport(EmailSettings.SMTP_OPTIONS)
+    .sendMail({
+      from: EmailSettings.SMTP_FROM,
+      to,
+      subject,
+      text,
+    })
+    .catch(() => {
+      logger.error("Failed to send email notification!");
+    });
+}
diff --git a/server/src/settings.ts b/server/src/settings.ts
index bff7f48..33db60b 100644
--- a/server/src/settings.ts
+++ b/server/src/settings.ts
@@ -1,4 +1,8 @@
 import { AppSettingsDto, asHyperlinkDto, isOAuthType, OAUTH_TYPES, OAuthProvider, OAuthType } from "@fumix/fu-blog-common";
+import { createTransport } from "nodemailer";
+import SMTPTransport from "nodemailer/lib/smtp-transport/index.js";
+import { LeveledLogMethod } from "winston";
+import logger from "./logger.js";
 import console from "console";
 import { readFileSync } from "fs";
 import path, { dirname } from "path";
@@ -50,6 +54,65 @@ export class DatabaseSettings {
   static readonly NAME: string = process.env.DATABASE_NAME ?? "fublog";
 }
 
+const securityTypes = ["STARTTLS", "TLS"] as const;
+type SmtpSecurity = (typeof securityTypes)[number];
+
+function isSmtpSecurity(s: string): s is SmtpSecurity {
+  return securityTypes.includes(s as SmtpSecurity);
+}
+
+export class EmailSettings {
+  static readonly SMTP_HOST: string | undefined = toNonBlankString(process.env.EMAIL_SMTP_HOST);
+  static readonly SMTP_FROM: string | undefined = toNonBlankString(process.env.EMAIL_SMTP_FROM);
+  static readonly SMTP_USER: string | undefined = toNonBlankString(process.env.EMAIL_SMTP_USER);
+  static readonly SMTP_PASSWORD: string | undefined = toNonBlankString(process.env.EMAIL_SMTP_PASSWORD);
+  static readonly SMTP_SECURITY: SmtpSecurity | undefined = toEnumValue(
+    process.env.EMAIL_SMTP_SECURITY,
+    (it) => (isSmtpSecurity(it) ? it : undefined),
+    "TLS",
+  );
+  static readonly SMTP_PORT: number = toNumberOrDefault(
+    process.env.EMAIL_SMTP_PORT,
+    EmailSettings.SMTP_SECURITY === "STARTTLS" ? 587 : 465,
+  );
+
+  static readonly SMTP_OPTIONS: SMTPTransport.Options = {
+    host: this.SMTP_HOST,
+    port: this.SMTP_PORT,
+    secure: this.SMTP_SECURITY !== "STARTTLS",
+    requireTLS: AppSettings.IS_PRODUCTION,
+    from: this.SMTP_FROM,
+    auth:
+      this.SMTP_USER && this.SMTP_PASSWORD
+        ? {
+            user: this.SMTP_USER,
+            pass: this.SMTP_PASSWORD,
+          }
+        : undefined,
+  } as const;
+
+  static {
+    if (!this.SMTP_HOST || !this.SMTP_FROM) {
+      logger.warn(" 📭 ❓ No email server and/or email from address specified! The blog won't send any email notifications.");
+    } else {
+      if (AppSettings.IS_PRODUCTION && (!this.SMTP_USER || !this.SMTP_PASSWORD)) {
+        logger.warn(
+          " 📭 🗝 No username/password set for sending email! Are you sure, that your SMTP server does not need any authentication?",
+        );
+      }
+      createTransport(this.SMTP_OPTIONS).verify(function (error, success) {
+        const message = error
+          ? " 📭 ❌ Failed to establish SMTP connection for sending e-mails!"
+          : " 📬 ✅ Checked that SMTP connection for sending e-mails can be established";
+        const log: LeveledLogMethod = error ? logger.error : logger.info;
+        log(
+          `${message}: ${EmailSettings.SMTP_HOST}:${EmailSettings.SMTP_PORT} (${EmailSettings.SMTP_SECURITY}) ${EmailSettings.SMTP_OPTIONS.auth ? "with username/password" : "with NO AUTHENTICATION!"}`,
+        );
+      });
+    }
+  }
+}
+
 export class ServerSettings {
   static readonly API_PATH: string = process.env.SERVER_API_PATH ?? "/api";
   static readonly PORT: number = toNumberOrDefault(process.env.SERVER_PORT, 5000);
@@ -106,9 +169,33 @@ export class OpenAISettings {
   static readonly API_KEY: string | undefined = process.env.OPENAI_API_KEY;
 }
 
+function toNonBlankString(value: string | undefined | null): string | undefined {
+  const trimmed = value?.trim();
+  if ((trimmed?.length ?? 0) > 0) {
+    return trimmed;
+  }
+}
+
 function toNumberOrDefault(value: string | undefined | null, defaultValue: number): number {
   if (value === undefined || value === null) {
     return defaultValue;
   }
   return Number(value);
 }
+
+/**
+ * Converts a string value to an "enum value" (string union type).
+ *
+ * @template T the string union type, can include undefined in case the cast function
+ *   or the default value can yield `undefined`
+ * @param {string | undefined | null} value - The value to be converted.
+ * @param {(value: string) => T} cast - The function used to cast the value to the enum type.
+ * @param {T} defaultValue - The default value to be returned if the input value is undefined or null.
+ * @return {T} - The converted enum value.
+ */
+function toEnumValue<T extends string | undefined>(value: string | undefined | null, cast: (v: string) => T, defaultValue: T): T {
+  if (value === undefined || value === null) {
+    return defaultValue;
+  }
+  return cast(value);
+}