diff --git a/app/__init__.py b/app/__init__.py
index e63cd40..3f12961 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -1,8 +1,13 @@
+import os
 from flask import Flask
 from config import Config
+import logging
+from loggin.handlers import RotatingFileHandler
+from logging.handlers import SMTPHandler
 from flask_sqlalchemy import SQLAlchemy
 from flask_migrate import Migrate
 from flask_login import LoginManager
+from app import routes, models, errors
 
 app = Flask(__name__)
 app.config.from_object(Config)
@@ -16,4 +21,36 @@ login = LoginManager(app)
 # sets de default login view
 login.login_view = "login"
 
-from app import routes, models
+if not app.debug:
+    if app.config["MAIL_SERVER"]:
+        auth = None
+        if app.config["MAIL_USERNAME"] or app.config["MAIL_PASSWORD"]:
+            auth = (app.config["MAIL_USERNAME"], app.config["MAIL_PASSWORD"])
+        secure = None
+        if app.config["MAIL_USE_TLS"]:
+            secure = ()
+        mail_handler = SMTPHandler(
+            mailhost=(app.config["MAIL_SERVER"], app.config["MAIL_PORT"]),
+            fromaddr="no-reply@" + app.config["MAIL_SERVER"],
+            toaddrs=app.config["ADMINS"],
+            subject="Microblog Failure",
+            credentials=auth,
+            secure=secure,
+        )
+        mail_handler.setLevel(logging.ERROR)
+        app.logger.addHandler(mail_handler)
+    if not os.path.exists("logs"):
+        os.mkdir("logs")
+    file_handler = RotatingFileHandler(
+        "logs/microblog.log", maxBytes=10240, backupCount=10
+    )
+    file_handler.setFormatter(
+        logging.Formatter(
+            "%(asctime)s %(levelname)s: %(message)s [in %(pathname)s:%(lineno)d]"
+        )
+    )
+    file_handler.setLevel(logging.INFO)
+    app.logger.addHandler(file_handler)
+
+    app.logger.setLevel(logging.INFO)
+    app.logger.info("Microblog startup")
diff --git a/app/errors.py b/app/errors.py
new file mode 100644
index 0000000..447c6cd
--- /dev/null
+++ b/app/errors.py
@@ -0,0 +1,13 @@
+from flask import render_template
+from app import app, db
+
+
+@app.errorhandler(404)
+def not_found_error(error):
+    return render_template("404.html"), 404
+
+
+@app.errorhandler(500)
+def internal_error(error):
+    db.session.rollback()
+    return render_template("500.html"), 500
diff --git a/app/forms.py b/app/forms.py
index 87b0da3..f62d31a 100644
--- a/app/forms.py
+++ b/app/forms.py
@@ -47,3 +47,13 @@ class EditProfileForm(FlaskForm):
     username = StringField("Username", validators=[DataRequired()])
     about_me = TextAreaField("About me", validators=[Length(min=0, max=140)])
     submit = SubmitField("Submit")
+
+    def __init__(self, original_username, *args, **kwargs):
+        super(EditProfileForm, self).__init__(*args, **kwargs)
+        self.original_username = original_username
+
+    def validate_username(self, username):
+        if username.data != self.original_username:
+            user = User.query.filter_by(username=self.username.data).first()
+            if user is not None:
+                raise ValidationError("Please use a different username.")
diff --git a/app/routes.py b/app/routes.py
index 1ef9c86..1272572 100644
--- a/app/routes.py
+++ b/app/routes.py
@@ -81,7 +81,7 @@ def user(username):
 @app.route("/edit_profile", methods=["GET", "POST"])
 @login_required
 def edit_profile():
-    form = EditProfileForm()
+    form = EditProfileForm(current_user.username)
     if form.validate_on_submit():
         current_user.username = form.username.data
         current_user.about_me = form.about_me.data
diff --git a/app/templates/404.html b/app/templates/404.html
new file mode 100644
index 0000000..9655dd8
--- /dev/null
+++ b/app/templates/404.html
@@ -0,0 +1,8 @@
+{% extends 'base.html' %}
+
+{% block content %}
+  <h1>File Not Found</h1>
+  <p>
+    <a href="{{ url_for('index') }}">Back</a>
+  </p>
+{% endblock %}
diff --git a/app/templates/500.html b/app/templates/500.html
new file mode 100644
index 0000000..0f1eba7
--- /dev/null
+++ b/app/templates/500.html
@@ -0,0 +1,9 @@
+{% extends 'base.html' %}
+
+{% block content %}
+  <h1>An unexpected error has occurred</h1>
+  <p>The administrator has been notified. Sorry for the inconvenience!</p>
+  <p>
+    <a href="{{ url_for('index') }}">Back</a>
+  </p>
+{% endblock %}
diff --git a/config.py b/config.py
index 694181f..6bed8d8 100644
--- a/config.py
+++ b/config.py
@@ -9,3 +9,9 @@ class Config(object):
         "DATABASE_URL"
     ) or "sqlite:///" + os.path.join(basedir, "app.db")
     SQLALCHEMY_TRACK_MODIFICATIONS = False
+    MAIL_SERVER = os.environ.get("MAIL_SERVER")
+    MAIL_PORT = int(os.environ.get("MAIL_PORT") or 25)
+    MAIL_USE_TLS = os.environ.get("MAIL_USE_TLS") is not None
+    MAIL_USERNAME = os.environ.get("MAIL_USERNAME")
+    MAIL_PASSWORD = os.environ.get("MAIL_PASSWORD")
+    ADMINS = ["your-email@example.com"]