smtp

Documentation

Index

• func GenerateDKIMKeyPair() (privateKeyPEM []byte, dnsRecord string, err error)
• type Attachment
• type Client
  • func NewClient(cfg ClientConfig) *Client
  • func (c *Client) Send(email *OutboundEmail) error
  • func (c *Client) SetDialer(d SMTPDialer)
  • func (c *Client) SetResolver(r MXResolver)
• type ClientConfig
• type DKIMSigner
  • func NewDKIMSigner(domain, selector, keyPath string) (*DKIMSigner, error)
  • func NewDKIMSignerFromKey(domain, selector string, key crypto.Signer) *DKIMSigner
  • func NewDKIMSignerFromPEM(domain, selector string, pemData []byte) (*DKIMSigner, error)
  • func (ds *DKIMSigner) Sign(msg []byte) ([]byte, error)
• type InboundEmail
• type InboundHandler
• type MXResolver
• type OutboundEmail
• type ParsedMIME
  • func ParseMIME(raw []byte) (*ParsedMIME, error)
• type SMTPDialer
• type Server
  • func NewServer(cfg ServerConfig, handler InboundHandler) *Server
  • func (s *Server) Addr() net.Addr
  • func (s *Server) Start() error
  • func (s *Server) Stop(ctx context.Context) error
• type ServerConfig
  • func DefaultServerConfig(domain string) ServerConfig

Functions

func GenerateDKIMKeyPair

func GenerateDKIMKeyPair() (privateKeyPEM []byte, dnsRecord string, err error)

GenerateDKIMKeyPair generates a new RSA-2048 key pair for DKIM signing. Returns the private key PEM and the public key DNS TXT record value.

Types

type Attachment

type Attachment struct {
	Filename    string
	ContentType string
	Data        []byte
}

Attachment represents an email attachment.

type Client

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

Client sends outbound emails.

func NewClient

func NewClient(cfg ClientConfig) *Client

NewClient creates an outbound SMTP client.

func (*Client) Send

func (c *Client) Send(email *OutboundEmail) error

Send delivers an outbound email. If a relay host is configured, delivery goes through the authenticated smarthost. Otherwise, direct MX is used.

func (*Client) SetDialer

func (c *Client) SetDialer(d SMTPDialer)

SetDialer replaces the SMTP dialer (for testing).

func (*Client) SetResolver

func (c *Client) SetResolver(r MXResolver)

SetResolver replaces the MX resolver (for testing).

type ClientConfig

type ClientConfig struct {
	// FromDomain is the bridge's email domain for the From address.
	FromDomain string
	// DKIMSigner signs outbound messages. Nil disables DKIM.
	DKIMSigner *DKIMSigner

	// RelayHost is the SMTP smarthost for outbound delivery.
	// If empty, direct MX delivery is used.
	RelayHost string
	// RelayPort is the smarthost port (typically 587 for STARTTLS).
	RelayPort int
	// RelayUsername is the SMTP AUTH username.
	RelayUsername string
	// RelayPassword is the SMTP AUTH password.
	RelayPassword string

	// MXPort overrides the port used for direct MX delivery.
	// If zero (default), tries 2525 then falls back to 25.
	MXPort int
}

ClientConfig holds outbound SMTP client configuration.

type DKIMSigner

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

DKIMSigner signs outbound emails with a DKIM signature.

func NewDKIMSigner

func NewDKIMSigner(domain, selector, keyPath string) (*DKIMSigner, error)

NewDKIMSigner creates a DKIM signer from a PEM-encoded RSA private key file.

func NewDKIMSignerFromKey

func NewDKIMSignerFromKey(domain, selector string, key crypto.Signer) *DKIMSigner

NewDKIMSignerFromKey creates a DKIM signer from an in-memory key. Useful for testing.

func NewDKIMSignerFromPEM

func NewDKIMSignerFromPEM(domain, selector string, pemData []byte) (*DKIMSigner, error)

NewDKIMSignerFromPEM creates a DKIM signer from PEM-encoded key bytes.

func (*DKIMSigner) Sign

func (ds *DKIMSigner) Sign(msg []byte) ([]byte, error)

Sign adds a DKIM-Signature header to the message. Returns the signed message bytes.

type InboundEmail

type InboundEmail struct {
	From       string
	To         []string
	RawMessage []byte
	ReceivedAt time.Time
}

InboundEmail represents a parsed inbound email ready for bridge processing.

type InboundHandler

type InboundHandler func(email *InboundEmail) error

InboundHandler is called when a valid inbound email is received.

type MXResolver

type MXResolver func(domain string) ([]*net.MX, error)

MXResolver looks up MX records for a domain. The default is net.LookupMX.

type OutboundEmail

type OutboundEmail struct {
	From    string   // e.g., "npub1abc@relay.example.com"
	To      []string // recipient email addresses
	Cc      []string
	Bcc     []string
	Subject string
	Body    string
}

OutboundEmail represents an email to be sent.

type ParsedMIME

type ParsedMIME struct {
	From        string
	To          []string
	Cc          []string
	Subject     string
	MessageID   string
	InReplyTo   string
	TextPlain   string
	TextHTML    string
	Attachments []Attachment
}

ParsedMIME represents a parsed email message.

func ParseMIME

func ParseMIME(raw []byte) (*ParsedMIME, error)

ParseMIME parses a raw email message into structured fields.

type SMTPDialer

type SMTPDialer func(addr string) (*gosmtp.Client, error)

SMTPDialer connects to an SMTP server. The default is gosmtp.Dial.

type Server

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

Server wraps go-smtp to receive inbound emails for the bridge.

func NewServer

func NewServer(cfg ServerConfig, handler InboundHandler) *Server

NewServer creates an SMTP server with the given configuration. The handler is called for each valid inbound email.

func (*Server) Addr

func (s *Server) Addr() net.Addr

Addr returns the listener's address, useful for tests.

func (*Server) Start

func (s *Server) Start() error

Start begins listening for SMTP connections.

func (*Server) Stop

func (s *Server) Stop(ctx context.Context) error

Stop gracefully shuts down the SMTP server.

type ServerConfig

type ServerConfig struct {
	// Domain is the bridge's email domain (e.g., "relay.example.com").
	Domain string
	// ListenAddr is the address to listen on (e.g., "0.0.0.0:2525").
	ListenAddr string
	// MaxMessageBytes is the maximum message size (default: 25MB).
	MaxMessageBytes int64
	// MaxRecipients is the maximum recipients per message (default: 10).
	MaxRecipients int
	// ReadTimeout is the per-command read timeout (default: 60s).
	ReadTimeout time.Duration
	// WriteTimeout is the per-command write timeout (default: 60s).
	WriteTimeout time.Duration
}

ServerConfig holds SMTP server configuration.

func DefaultServerConfig

func DefaultServerConfig(domain string) ServerConfig

DefaultServerConfig returns sensible defaults for the SMTP server.