5 SMTP: Sending E-Mail

(require net/smtp)

The net/smtp module provides tools for sending electronic mail messages using SMTP. The client must provide the address of an SMTP server; in contrast, the net/sendmail module uses a pre-configured sendmail on the local system.

The net/head library defines the format of a header string, which is used by send-smtp-message. The net/head module also provides utilities to verify the formatting of a mail address. The procedures of the net/smtp module assume that the given string arguments are well-formed.

5.1 SMTP Functions

(smtp-send-message   server-address             from             to             header             message            [ #:port-no port-no/k             #:auth-user user             #:auth-passwd pw             #:tcp-connect connect             #:tls-encode encode             port-no])   →   void?

server-address : string?

from : string?

to : (listof string?)

header : string?

message : (listof (or/c string? bytes?))

port-no/k : (integer-in 0 65535) = 25

user : (or/c string? false/c) = #f

pw : (or/c string? false/c) = #f

connect   :   ((string? (integer-in 0 65535))  . ->* . (input-port? output-port?))   =   tcp-connect

encode   :   (or/c false/c       ((input-port? output-port?         #:mode (one-of/c 'connect)         #:encrypt (one-of/c 'tls)         #:close-original? (one-of/c #t))        . ->* . (input-port? output-port?)))   =   #f

port-no : (integer-in 0 65535) = port-no/k

Connects to the server at server-address and port-no to send a message. The from argument specifies the mail address of the sender, and to is a list of recipient addresses (including “To:”, “CC”, and “BCC” recipients).

The header argument is the complete message header, which should already include “From:”, “To:”, and “CC:” fields consistent with the given sender and recipients. See also the net/head library for header-creating utilities.

The message argument is the body of the message, where each string or byte string in the list corresponds to a single line of message text. No string in message should contain a carriage return or linefeed character.

The optional port-no argument – which can be specified either with the #:port-no keyword or, for backward compatibility, as an extra argument after keywords – specifies the IP port to use in contacting the SMTP server.

The optional #:auth-user and #:auth-passwd keyword argument supply a username and password for authenticated SMTP (using the AUTH PLAIN protocol).

The optional #:tcp-connect keyword argument supplies a connection procedure to be used in place of tcp-connect. For example, use ssl-connect to connect to the server via SSL.

If the optional #:tls-encode keyword argument supplies a procedure instead of #f, then the ESMTP STARTTLS protocol is used to initiate SSL communication with the server. The procedure given as the #:tls-encode argument should be like ports->ssl-ports; it will be called as

  (encode r w #:mode 'connect #:encrypt 'tls #:close-original? #t)

and it should return two values: an input port and an export port. All further SMTP communication uses the returned ports.

For encrypted communication, normally either ssl-connect should be supplied for #:tcp-connect, or ports->ssl-ports should be supplied for #:tls-encode – one or the other (depending on what the server expects), rather than both.

(smtp-sending-end-of-message) → (-> any)

(smtp-sending-end-of-message proc) → void?

proc : (-> any)

A parameter that determines a send-done procedure to be called after smtp-send-message has completely sent the message. Before the send-done procedure is called, breaking the thread that is executing smtp-send-message cancels the send. After the send-done procedure is called, breaking may or may not cancel the send (and probably will not).

5.2 SMTP Unit

(require net/smtp-unit)

smtp@ : unit?

Imports nothing, exports smtp^.

5.3 SMTP Signature

(require net/smtp-sig)

smtp^ : signature

Includes everything exported by the net/smtp module.