- Fixed statement about setting `config.action_mailer.default_url_options = {protocol: 'https'}` . We are just setting the protocol key to 'https', not replacing/initializing the complete config.
- Fixed grammar in assert_emails changlog
- Added sentence separator for code ":"

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They would be lost when the delivery job is enqueued, otherwise.
Prevents a common, hard-to-find bug like:

```ruby
message = Notifier.welcome(user, foo)
message.message_id = my_generated_message_id
message.deliver_later
```

The message_id is silently lost here! *Only the mailer arguments are
passed to the delivery job.*

This raises an exception now.

Make modifications to the message within the mailer method or use a
custom Active Job to manage delivery instead of using #deliver_later.

Removes `-t`

Adds changelog headers for beta3 release

Whenever you are sending emails in integration tests using the `:test`
delivery method you need to make sure that
`ActionMailer::Base.deliveries` is reset after every test. This piece of
boilerplate code is present in all my applications that send
emails. Let's have `ActionDispatch::IntegrationTest` reset the
deliveries automatically.

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During the `5.0.0.beta1` release, the CHANGELOGs got an entry like the
following:

```
* No changes.
```

It is kinda confusing as there are indeed changes after it. Not a
biggie, just a small pass over the CHANGELOGs.

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This reverts commit 65a61ab7, reversing
changes made to 14314ca1.

This PR broke the build

`config.force_ssl = true` will set
config.action_mailer.default_url_options = { protocol: 'https' }

If you have turned on force_ssl, and then gone to the effort of setting
config.action_mailer.default_url_options = {host: 'example.com'} then
you are probably pointing people back to your current app and want
https on that too.

This reverts commit f2a8c236, reversing
changes made to 3046c9bb.

When #deliver_now is called all translations within the
generated email will be looked up for the current I18n
locale.

    I18n.locale = ‘de’
    mail.deliver_now # Generates german email, correct

In #enqueue_delivery the locale was not considered and
the resulting job uses the default locale.

    I18n.locale = ‘de’
    mail.deliver_later # Generate english email, incorrect

In order to achieve a consistent behaviour the current locale
is now always passed to `ActionMailer::DeliveryJob`.

Also add a CHANGELOG entry for #18587

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Use a preview interceptor to search for inline cid: urls in src
attributes and convert them to data urls.

Mailer preview now uses `url_for` to fix links to emails for apps running on a subdirectory, closes #19092.

While this was true before when every `dd` had a value,
this patch makes sure that everything keeps lining up even
when the `dd` node is blank.

One or multiple mail interceptors can be unregistered using
`ActionMailer::Base.unregister_interceptors` or
`ActionMailer::Base.unregister_interceptor`.

For preview interceptors, it's possible to use
`ActionMailer::Base.unregister_preview_interceptors` or
`ActionMailer::Base.unregister_preview_interceptor`.

Refactors logic to constantize a string/symbol into separate method.

Following the same naming convention used in
controllers and jobs.

These methods were deprecated in Rails 4.2 (see f4ee1147) so they can
be safely removed in Rails 5.0.

Given the following templates:

    mailer/demo.html.erb
    mailer/demo.en.html.erb
    mailer/demo.pt.html.erb

Before this change for a locale that doesn't have its related file
the `mailer/demo.html.erb` will
be rendered even if `en` is the default locale.

Now `mailer/demo.en.html.erb` has precedence over the file without
 locale.

Also, it is possible to give a fallback.

    mailer/demo.pt.html.erb
    mailer/demo.pt-BR.html.erb

So if the locale is `pt-PT`, `mailer/demo.pt.html.erb` will be
 rendered given the right I18n fallback configuration.

Fixes #11884.

We will support only Ruby >= 2.1.

But right now we don't accept pull requests with syntax changes to drop
support to Ruby 1.9.

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