bundle install ができない

bundle installをしたのですが

err文
Resolving dependencies...
Bundler could not find compatible versions for gem "actionmailbox":
  In snapshot (Gemfile.lock):
    actionmailbox (= 6.0.4)

  In Gemfile:
    rails (~> 6.0.4) was resolved to 6.0.4.8, which depends on
      actionmailbox (= 6.0.4.8)

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.

Gemfile
source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

gem 'rails',      '~>6.0.4'
gem 'puma',       '~>4.3.6'
gem 'sass-rails', '~>5.1.0'
gem 'webpacker',  '~>4.0.7'
gem 'turbolinks', '~>5.2.0'
gem 'jbuilder',   '~>2.9.1'
gem 'bootsnap',   '~>1.10.3', require: false

group :development, :test do
  gem 'sqlite3', '1.4.1'
  gem 'byebug',  '11.0.1', platforms: [:mri, :mingw, :x64_mingw]
end

group :development do
  gem 'web-console',           '4.0.1'
  gem 'listen',                '3.1.5'
  gem 'spring',                '2.1.0'
  gem 'spring-watcher-listen', '2.0.1'
end

group :test do
  gem 'capybara',                 '3.28.0'
  gem 'selenium-webdriver',       '3.142.4'
  gem 'webdrivers',               '4.1.2'
  gem 'rails-controller-testing', '1.0.4'
  gem 'minitest',                 '5.15.0'
  gem 'minitest-reporters',       '1.3.8'
  gem 'guard',                    '2.16.2'
  gem 'guard-minitest',           '2.4.6'
end

group :production do
  gem 'pg', '1.1.4'
end
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]