An adapter that sends email using the SMTP protocol.

Underneath this adapter uses the 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