# `Swoosh.Adapters.SMTP`
[🔗](https://github.com/swoosh/swoosh/blob/v1.27.0/lib/swoosh/adapters/smtp.ex#L1)

An adapter that sends email using the SMTP protocol.

Underneath this adapter uses the
[gen_smtp](https://github.com/gen-smtp/gen_smtp) library, add it to your mix.exs file.

## Example

    # mix.exs
    def deps do
      [
       {:swoosh, "~> 1.3"},
       {:gen_smtp, "~> 1.1"}
      ]
    end

    # config/config.exs
    config :sample, Sample.Mailer,
      adapter: Swoosh.Adapters.SMTP,
      relay: "smtp.avengers.com",
      username: "tonystark",
      password: "ilovepepperpotts",
      ssl: true,
      tls: :always,
      # See "TLS options and certificate verification" below.
      auth: :always,
      port: 1025,
      dkim: [
        s: "default", d: "domain.com",
        private_key: {:pem_plain, File.read!("priv/keys/domain.private")}
      ],
      retries: 2,
      no_mx_lookups: false

    # lib/sample/mailer.ex
    defmodule Sample.Mailer do
      use Swoosh.Mailer, otp_app: :sample
    end

## Note

With `STARTTLS` you should omit the ssl configuration or set it to false.

## TLS options and certificate verification

When using STARTTLS (`tls: :always`, with `ssl` omitted or set to `false`),
you can pass `tls_options` directly to `gen_smtp` to enable certificate path
validation:

    config :sample, Sample.Mailer,
      adapter: Swoosh.Adapters.SMTP,
      relay: "smtp.avengers.com",
      tls: :always,
      tls_options: [
        versions: [:"tlsv1.2", :"tlsv1.3"],
        verify: :verify_peer,
        cacerts: :public_key.cacerts_get(),
        server_name_indication: ~c"smtp.avengers.com",
        depth: 99,
        customize_hostname_check: [
          match_fun: :public_key.pkix_verify_hostname_match_fun(:https)
        ]
      ]

For implicit TLS (`ssl: true`, typically on port 465), `gen_smtp` uses
`sockopts` for the initial SSL connection instead of `tls_options`:

    config :sample, Sample.Mailer,
      adapter: Swoosh.Adapters.SMTP,
      relay: "smtp.avengers.com",
      ssl: true,
      port: 465,
      sockopts: [
        versions: [:"tlsv1.2", :"tlsv1.3"],
        verify: :verify_peer,
        cacerts: :public_key.cacerts_get(),
        server_name_indication: ~c"smtp.avengers.com",
        depth: 99,
        customize_hostname_check: [
          match_fun: :public_key.pkix_verify_hostname_match_fun(:https)
        ]
      ]

`:public_key.cacerts_get/0` is available on OTP 25 and later. For older OTP
releases, or when using a package such as `castore`, pass `cacertfile` or
`cacerts` instead.

Using the appropriate option for the connection type silences OTP's
"Authenticity is not established by certificate path validation" warning by
actually configuring peer certificate verification.

For more details, please see [gen_smtp docs](https://hexdocs.pm/gen_smtp/readme.html)

# `deliver`

# `gen_smtp_config`

# `validate_config`

# `validate_dependency`

---

*Consult [api-reference.md](api-reference.md) for complete listing*