modules/mail/smtp

Package smtp sends email through any SMTP server: Amazon SES, Postmark, Mailgun, Google Workspace, your own server, or Mailpit in development (ADR-0025, ADR-0037).

sender, err := smtp.New("smtp.example.com:587",
	smtp.WithAuth(cfg.SMTPUsername, cfg.SMTPPassword),
)

Each Send opens a connection, delivers one message and closes it. Permanent refusals (5xx replies) wrap mail.ErrRejected; everything else is temporary and safe to retry.

Stability: pre-1.0 (ADR-0015).

Constants#

const DefaultTimeout#

const DefaultTimeout = 30 * time.Second

DefaultTimeout bounds one delivery: connecting, authenticating and sending.

Types#

type Option#

type Option interface {
	// contains filtered or unexported methods
}

An Option configures New.

func WithAuth#

func WithAuth(username string, password config.Secret) Option

WithAuth authenticates with username and password (SMTP AUTH PLAIN), only over an encrypted connection or to a local server.

func WithLocalName#

func WithLocalName(name string) Option

WithLocalName sets the host name sent in EHLO. Default: "localhost".

func WithTLS#

func WithTLS(mode TLSMode) Option

WithTLS sets how the connection is encrypted. Default: TLSStartTLS.

func WithTLSConfig#

func WithTLSConfig(cfg *tls.Config) Option

WithTLSConfig sets the TLS configuration, for example to trust a private certificate authority. Default: system roots, TLS 1.2 or later.

func WithTimeout#

func WithTimeout(d time.Duration) Option

WithTimeout bounds each delivery. Default: DefaultTimeout.

type Sender#

type Sender struct {
	// contains filtered or unexported fields
}

Sender delivers email over SMTP. It is safe for concurrent use.

func New#

func New(addr string, opts ...Option) (*Sender, error)

New returns a sender for the server at addr ("host:port").

func (*Sender) Send#

func (s *Sender) Send(ctx context.Context, m mail.Message) error

Send delivers m. Tags are not sent: SMTP has no standard for them.

type TLSMode#

type TLSMode string

TLSMode is how the connection is encrypted.

const TLSStartTLS, …#

const (
	// TLSStartTLS connects in plain text, then requires STARTTLS before
	// authenticating or sending. Usually port 587.
	TLSStartTLS TLSMode = "starttls"
	// TLSImplicit uses TLS from the first byte. Usually port 465.
	TLSImplicit TLSMode = "tls"
	// TLSNone never encrypts. Use it only for local servers such as Mailpit.
	TLSNone TLSMode = "none"
)

TLS modes.

func ParseTLSMode#

func ParseTLSMode(s string) (TLSMode, error)

ParseTLSMode parses "starttls", "tls" or "none".