diff --git a/.djlintrc b/.djlintrc
new file mode 100644
index 0000000..a5811ae
--- /dev/null
+++ b/.djlintrc
@@ -0,0 +1,4 @@
+{
+	"profile": "jinja",
+	"ignore": "D018"
+}
diff --git a/Cargo.lock b/Cargo.lock
index 662bc02..42bc0cf 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1277,6 +1277,7 @@ dependencies = [
  "openidconnect",
  "parking_lot",
  "serde",
+ "serde_urlencoded",
  "sqlx",
  "tera",
  "thiserror",
diff --git a/Cargo.toml b/Cargo.toml
index 7000315..fe6bcc9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,6 +16,7 @@ once_cell = "1.18.0"
 openidconnect = "3.3.0"
 parking_lot = "0.12.1"
 serde = { version = "1.0.183", features = ["derive"] }
+serde_urlencoded = "0.7.1"
 sqlx = { version = "0.7.1", features = ["runtime-tokio", "postgres", "uuid", "migrate"] }
 tera = "1.19.0"
 thiserror = "1.0.44"
diff --git a/src/main.rs b/src/main.rs
index c99d97f..31d0051 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,6 @@
 use std::{
     collections::{HashMap, VecDeque},
+    fmt::Display,
     net::SocketAddr,
     sync::Arc,
 };
@@ -119,6 +120,8 @@ struct Settings {
     address: String,
     database_url: String,
 
+    mail_domain: String,
+
     domain: String,
 
     oidc_endpoint: String,
@@ -314,6 +317,7 @@ impl OpenidConnector {
 struct AppState {
     jwt_secret: HS256Key,
     db: PgPool,
+    mail_domain: String,
     oidc: OpenidConnector,
 }
 
@@ -486,33 +490,42 @@ where
     }
 }
 
-#[derive(Serialize, Deserialize)]
+#[derive(Serialize, Deserialize, Debug)]
 struct Mail {
     mail: String,
 }
 
-async fn home(state: State<Arc<AppState>>, User(user): User) -> Result<Html<String>, Error> {
+#[derive(Serialize, Deserialize)]
+struct HomeQuery {
+    user_error: Option<UserError>,
+}
+
+async fn home(
+    state: State<Arc<AppState>>,
+    User(user): User,
+    Query(query): Query<HomeQuery>,
+) -> Result<Html<String>, Error> {
     let mails = sqlx::query_as!(Mail, "SELECT mail FROM emails WHERE id = $1", user)
         .fetch_all(&state.db)
         .await?;
 
     let mut context = tera::Context::new();
     context.insert("mails", &mails);
+    context.insert("mail_domain", &state.mail_domain);
+    if let Some(err) = query.user_error {
+        tracing::info!("User error: {err:?}");
+        context.insert("user_error", &err.to_string());
+    }
     context.extend(global_context());
 
     Ok(Html(TEMPLATES.render("home.html", &context)?))
 }
 
-#[derive(Deserialize, Debug)]
-struct MailDelete {
-    mail: String,
-}
-
 #[tracing::instrument(skip(state))]
 async fn delete_mail(
     state: State<Arc<AppState>>,
     User(user): User,
-    Form(delete): Form<MailDelete>,
+    Form(delete): Form<Mail>,
 ) -> Result<Redirect, Error> {
     let rows_affected = sqlx::query!(
         "DELETE FROM emails WHERE id = $1 AND mail = $2",
@@ -531,6 +544,57 @@ async fn delete_mail(
     Ok(Redirect::to("/"))
 }
 
+#[derive(Serialize, Deserialize, Debug)]
+enum UserError {
+    MailAlreadyExists,
+}
+
+impl Display for UserError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            UserError::MailAlreadyExists => {
+                write!(f, "email address is already used by another user")
+            }
+        }
+    }
+}
+
+async fn add_mail(
+    state: State<Arc<AppState>>,
+    User(user): User,
+    Form(add): Form<Mail>,
+) -> Result<Redirect, Error> {
+    let has_mail = sqlx::query!(
+        "SELECT COUNT(*) FROM emails WHERE id != $1 AND mail = $2",
+        user,
+        add.mail
+    )
+    .fetch_one(&state.db)
+    .await?
+    .count
+    .expect("count should not be null");
+
+    if has_mail != 0 {
+        Ok(Redirect::to(&format!(
+            "/?{}",
+            serde_urlencoded::to_string(&HomeQuery {
+                user_error: Some(UserError::MailAlreadyExists)
+            })
+            .expect("could not generate query")
+        )))
+    } else {
+        sqlx::query!(
+            "INSERT INTO emails (id, mail) VALUES ($1, $2) ON CONFLICT DO NOTHING",
+            user,
+            add.mail
+        )
+        .execute(&state.db)
+        .await?;
+
+        Ok(Redirect::to("/"))
+    }
+}
+
 #[tokio::main]
 async fn main() -> color_eyre::Result<()> {
     color_eyre::install()?;
@@ -562,11 +626,13 @@ async fn main() -> color_eyre::Result<()> {
         .route("/login/redirect/:id", get(redirected))
         .route("/", get(home))
         .route("/mail/delete", post(delete_mail))
+        .route("/mail/add", post(add_mail))
         .fallback(page_not_found)
         .with_state(Arc::new(AppState {
             db,
             oidc,
             jwt_secret: config.jwt_secret.0,
+            mail_domain: config.mail_domain,
         }));
 
     Ok(axum::Server::bind(&addr)
diff --git a/templates/home.html b/templates/home.html
index 6ae1723..5e85a71 100644
--- a/templates/home.html
+++ b/templates/home.html
@@ -8,6 +8,7 @@
 {% block content %}
     <div class="container">
         <h1 class="title is-1">Mail management</h1>
+        {% if user_error %}<div class="alert alert-danger">{{ user_error }}</div>{% endif %}
         <h2 class="title is-2">Mails</h2>
         <ul class="list-group">
             {% for mail in mails %}
@@ -43,5 +44,50 @@
                 </li>
             {% endfor %}
         </ul>
+        <button type="button"
+                class="btn btn-primary mt-2"
+                data-bs-toggle="modal"
+                data-bs-target="#mailAdd">Add new mail</button>
+        <div class="modal fade"
+             tabindex="-1"
+             id="mailAdd"
+             aria-labelledby="mailAddLabel">
+            <div class="modal-dialog">
+                <div class="modal-content">
+                    <div class="modal-header">
+                        <h1 class="modal-title fs-5" id="mailAddLabel">Add new mail</h1>
+                        <button type="button"
+                                class="btn-close"
+                                data-bs-dismiss="modal"
+                                aria-label="Close"></button>
+                    </div>
+                    <div class="modal-body">
+                        <form action="/mail/add" method="post" id="mailAddForm">
+                            <div class="form-floating mb-3">
+                                <input type="email"
+                                       class="form-control"
+                                       id="floatingAddMail"
+                                       placeholder="mail@{{ mail_domain }}"
+                                       name="mail"
+                                       value="@{{ mail_domain }}">
+                                <label for="floatingAddMail">Email address</label>
+                            </div>
+                        </form>
+                    </div>
+                    <div class="modal-footer">
+                        <button type="button" class="btn btn-secondary" data-bs-dismiss="modal">Cancel</button>
+                        <button type="submit" class="btn btn-primary" form="mailAddForm">Add</button>
+                    </div>
+                </div>
+            </div>
+        </div>
     </div>
+    <script>
+		const addModal = document.getElementById('mailAdd')
+		const addInput = document.getElementById('floatingAddMail')
+
+		addModal.addEventListener('shown.bs.modal', () => {
+			addInput.focus()
+		})
+    </script>
 {% endblock content %}