diff --git a/README.md b/README.md
index a576bca..e799bf6 100644
--- a/README.md
+++ b/README.md
@@ -50,3 +50,23 @@ tail -f /var/log/nagios4/telegram.log
 ```
 
 Log level can be raised using `--verbose` or even more with `--debug` arguments.
+
+
+## Message format
+
+`notify-by-telegram` script uses the `MarkdownV2` format to generate Telegram messages.
+
+[Jinja](https://jinja.palletsprojects.com) is used for templating (eg. replace `{{host_name}}` placeholders by the value submitted by Nagios).
+
+Default **host** and **service** templates can be found in the [templates](templates) directory.
+
+They can be overriden in the configuration file:
+
+```json
+{
+  "host_template": "/etc/nagios4/host.md.j2",
+  "service_template": "/etc/nagios4/service.md.j2"
+}
+```
+
+Both options are optional.
diff --git a/TODO.txt b/TODO.txt
index 216ec9e..12a5bc7 100644
--- a/TODO.txt
+++ b/TODO.txt
@@ -1,4 +1,3 @@
-Add host and service templates to configuration file (+doc)
 Factorize the template rendering functions
 Use JSON schema to validate configuration file
 Add pre-commit Dockerfile and a doc to easily lint the code
diff --git a/notify-by-telegram.py b/notify-by-telegram.py
index 8410ac2..2b5ebe6 100755
--- a/notify-by-telegram.py
+++ b/notify-by-telegram.py
@@ -18,32 +18,32 @@ def parse_arguments():
     parser = argparse.ArgumentParser()
     # base arguments
     parser.add_argument('-v', '--verbose', dest='loglevel', action='store_const', const=logging.INFO,
-                        help='Print more output')
+                        help='print more output')
     parser.add_argument('-d', '--debug', dest='loglevel', action='store_const', const=logging.DEBUG,
-                        default=logging.WARNING, help='Print even more output')
-    parser.add_argument('-c', '--config', help='Configuration file location', required=True)
-    parser.add_argument('-o', '--logfile', help='Logging file location')
-    subparsers = parser.add_subparsers(title='commands', dest='command', help='Nagios notification type')
+                        default=logging.WARNING, help='print even more output')
+    parser.add_argument('-c', '--config', help='configuration file location', required=True)
+    parser.add_argument('-o', '--logfile', help='logging file location')
+    subparsers = parser.add_subparsers(title='commands', dest='command', help='nagios notification type')
 
     # host notifications
     host_parser = subparsers.add_parser('host')
-    host_parser.add_argument('--notification-type', help='Nagios $NOTIFICATIONTYPE$', required=True)
-    host_parser.add_argument('--service-desc', help='Nagios $SERVICEDESC$', required=True)
-    host_parser.add_argument('--host-name', help='Nagios $HOSTNAME$', required=True)
-    host_parser.add_argument('--host-state', help='Nagios $HOSTSTATE$', required=True)
-    host_parser.add_argument('--host-address', help='Nagios $HOSTADDRESS$', required=True)
-    host_parser.add_argument('--host-output', help='Nagios $HOSTOUTPUT$', required=True)
-    host_parser.add_argument('--long-date-time', help='Nagios $LONGDATETIME$', required=True)
+    host_parser.add_argument('--notification-type', help='nagios $NOTIFICATIONTYPE$', required=True)
+    host_parser.add_argument('--service-desc', help='nagios $SERVICEDESC$', required=True)
+    host_parser.add_argument('--host-name', help='nagios $HOSTNAME$', required=True)
+    host_parser.add_argument('--host-state', help='nagios $HOSTSTATE$', required=True)
+    host_parser.add_argument('--host-address', help='nagios $HOSTADDRESS$', required=True)
+    host_parser.add_argument('--host-output', help='nagios $HOSTOUTPUT$', required=True)
+    host_parser.add_argument('--long-date-time', help='nagios $LONGDATETIME$', required=True)
 
     # service notifications
     service_parser = subparsers.add_parser('service')
-    service_parser.add_argument('--notification-type', help='Nagios $NOTIFICATIONTYPE$', required=True)
-    service_parser.add_argument('--service-desc', help='Nagios $SERVICEDESC$', required=True)
-    service_parser.add_argument('--host-alias', help='Nagios $HOSTALIAS$', required=True)
-    service_parser.add_argument('--host-address', help='Nagios $HOSTADDRESS$', required=True)
-    service_parser.add_argument('--service-state', help='Nagios $SERVICESTATE$', required=True)
-    service_parser.add_argument('--long-date-time', help='Nagios $LONGDATETIME$', required=True)
-    service_parser.add_argument('--service-output', help='Nagios $SERVICEOUTPUT$', required=True)
+    service_parser.add_argument('--notification-type', help='nagios $NOTIFICATIONTYPE$', required=True)
+    service_parser.add_argument('--service-desc', help='nagios $SERVICEDESC$', required=True)
+    service_parser.add_argument('--host-alias', help='nagios $HOSTALIAS$', required=True)
+    service_parser.add_argument('--host-address', help='nagios $HOSTADDRESS$', required=True)
+    service_parser.add_argument('--service-state', help='nagios $SERVICESTATE$', required=True)
+    service_parser.add_argument('--long-date-time', help='nagios $LONGDATETIME$', required=True)
+    service_parser.add_argument('--service-output', help='nagios $SERVICEOUTPUT$', required=True)
 
     args = parser.parse_args()
     return args
@@ -59,10 +59,10 @@ def read_config(filename=None):
 
 def validate_config(config):
     if config is None:
-        raise InvalidConfigException('Config is not a dict')
+        raise InvalidConfigException('config is not a dict')
     for key in ['chat_id', 'auth_key']:
         if key not in config:
-            raise InvalidConfigException(f'Missing "{key}" key in config')
+            raise InvalidConfigException(f'missing "{key}" key in config')
 
 
 def setup_logging(args):
@@ -76,12 +76,16 @@ def markdown_escape(text):
     return text
 
 
-def generate_host_payload(chat_id, args):
+def generate_host_payload(chat_id, args, template_file_name=None):
     payload = {'chat_id': chat_id, 'parse_mode': 'MarkdownV2'}
-    absolute_path = os.path.split(os.path.abspath(__file__))[0]
-    loader = FileSystemLoader(os.path.join(absolute_path, 'templates'))
+    if not template_file_name:
+        absolute_path = os.path.split(os.path.abspath(__file__))[0]
+        template_file_name = os.path.join(absolute_path, 'templates', 'host.md.j2')
+    template_path = os.path.dirname(os.path.abspath(template_file_name))
+    template_name = os.path.basename(os.path.abspath(template_file_name))
+    loader = FileSystemLoader(template_path)
     env = Environment(loader=loader)
-    template = env.get_template('host.md.j2')
+    template = env.get_template(template_name)
     text = template.render(notification_type=markdown_escape(args.notification_type),
                            host_name=markdown_escape(args.host_name), host_state=markdown_escape(args.host_state),
                            host_address=markdown_escape(args.host_address),
@@ -91,12 +95,16 @@ def generate_host_payload(chat_id, args):
     return payload
 
 
-def generate_service_payload(chat_id, args):
+def generate_service_payload(chat_id, args, template_file_name=None):
     payload = {'chat_id': chat_id, 'parse_mode': 'MarkdownV2'}
-    absolute_path = os.path.split(os.path.abspath(__file__))[0]
-    loader = FileSystemLoader(os.path.join(absolute_path, 'templates'))
+    if not template_file_name:
+        absolute_path = os.path.split(os.path.abspath(__file__))[0]
+        template_file_name = os.path.join(absolute_path, 'templates', 'service.md.j2')
+    template_path = os.path.dirname(os.path.abspath(template_file_name))
+    template_name = os.path.basename(os.path.abspath(template_file_name))
+    loader = FileSystemLoader(template_path)
     env = Environment(loader=loader)
-    template = env.get_template('service.md.j2')
+    template = env.get_template(template_name)
     text = template.render(notification_type=markdown_escape(args.notification_type),
                            service_desc=markdown_escape(args.service_desc), host_alias=markdown_escape(args.host_alias),
                            host_address=markdown_escape(args.host_address),
@@ -116,23 +124,28 @@ def send_message(auth_key, payload):
 
 
 def main():
-    args = parse_arguments()
-    setup_logging(args)
-    logger.info(f'reading configuration file {args.config}')
-    config = read_config(args.config)
-    logger.info('validating configuration')
-    validate_config(config)
+    try:
+        args = parse_arguments()
+        setup_logging(args)
+        logger.info(f'reading configuration file {args.config}')
+        config = read_config(args.config)
+        logger.info('validating configuration')
+        validate_config(config)
 
-    logger.info('generating payload')
-    if args.command == 'host':
-        payload = generate_host_payload(chat_id=config['chat_id'], args=args)
-    elif args.command == 'service':
-        payload = generate_service_payload(chat_id=config['chat_id'], args=args)
-    else:
-        raise NotImplementedError(f'Command {args.command} not supported')
+        logger.info('generating payload')
+        if args.command == 'host':
+            payload = generate_host_payload(chat_id=config['chat_id'], args=args,
+                                            template_file_name=config.get('host_template'))
+        elif args.command == 'service':
+            payload = generate_service_payload(chat_id=config['chat_id'], args=args,
+                                            template_file_name=config.get('service_template'))
+        else:
+            raise NotImplementedError(f'command {args.command} not supported')
 
-    logger.info('sending message to telegram api')
-    send_message(auth_key=config['auth_key'], payload=payload)
+        logger.info('sending message to telegram api')
+        send_message(auth_key=config['auth_key'], payload=payload)
+    except Exception as err:
+        logger.exception('cannot execute program')
 
 
 if __name__ == '__main__':