rails sでエンターキーを押すとエラーが出る

ruby on rails上"rails s"を押したところ下記のようなエラーが出ます。どのように対処すればよいでしょうか。どなたか回答よろしくお願いいたします。

You don't have net-smtp installed in your application. Please add it to your Gemfile and run bundle install
=> Booting Puma
=> Rails 6.1.6.1 application starting in development
=> Run bin/rails server --help for more startup options
Puma starting in single mode...

• Puma version: 5.6.4 (ruby 3.1.2-p20) ("Birdie's Version")
• Min threads: 5
• Max threads: 5
• Environment: development
• PID: 14863
• Listening on http://127.0.0.1:8080
• Listening on http://[::1]:8080

Use Ctrl-C to stop
^C- Gracefully stopping, waiting for requests to finish
=== puma shutdown: 2022-08-15 07:30:17 +0000 ===