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https://github.com/mailhog/smtp

MailHog SMTP Protocol
https://github.com/mailhog/smtp

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MailHog SMTP Protocol

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MailHog SMTP Protocol [![GoDoc](https://godoc.org/github.com/mailhog/smtp?status.svg)](https://godoc.org/github.com/mailhog/smtp) [![Build Status](https://travis-ci.org/mailhog/smtp.svg?branch=master)](https://travis-ci.org/mailhog/smtp)

=========



`github.com/mailhog/smtp` implements an SMTP server state machine.



It attempts to encapsulate as much of the SMTP protocol (plus its extensions) as possible

without compromising configurability or requiring specific backend implementations.



  * ESMTP server implementing [RFC5321](http://tools.ietf.org/html/rfc5321)

  * Support for:

    * AUTH [RFC4954](http://tools.ietf.org/html/rfc4954)

    * PIPELINING [RFC2920](http://tools.ietf.org/html/rfc2920)

    * STARTTLS [RFC3207](http://tools.ietf.org/html/rfc3207)



```go

proto := NewProtocol()

reply := proto.Start()

reply = proto.ProcessCommand("EHLO localhost")

// ...

```



See [MailHog-Server](https://github.com/mailhog/MailHog-Server) and [MailHog-MTA](https://github.com/mailhog/MailHog-MTA) for example implementations.



### Commands and replies



Interaction with the state machine is via:

* the `Parse` function

* the `ProcessCommand` and `ProcessData` functions



You can mix the use of all three functions as necessary.



#### Parse



`Parse` should be used on a raw text stream. It looks for an end of line (`\r\n`), and if found, processes a single command. Any unprocessed data is returned.



If any unprocessed data is returned, `Parse` should be

called again to process then next command.



```go

text := "EHLO localhost\r\nMAIL FROM:\r\nDATA\r\nTest\r\n.\r\n"



var reply *smtp.Reply

for {

  text, reply = proto.Parse(text)

  if len(text) == 0 {

    break

  }

}

```



#### ProcessCommand and ProcessData



`ProcessCommand` should be used for an already parsed command (i.e., a complete

SMTP "line" excluding the line ending).



`ProcessData` should be used if the protocol is in `DATA` state.



```go

reply = proto.ProcessCommand("EHLO localhost")

reply = proto.ProcessCommand("MAIL FROM:")

reply = proto.ProcessCommand("DATA")

reply = proto.ProcessData("Test\r\n.\r\n")

```



### Hooks



The state machine provides hooks to manipulate its behaviour.



See [![GoDoc](https://godoc.org/github.com/mailhog/smtp?status.svg)](https://godoc.org/github.com/mailhog/smtp) for more information.



| Hook                               | Description

| ---------------------------------- | -----------

| LogHandler                         | Called for every log message

| MessageReceivedHandler             | Called for each message received

| ValidateSenderHandler              | Called after MAIL FROM

| ValidateRecipientHandler           | Called after RCPT TO

| ValidateAuthenticationHandler      | Called after AUTH

| SMTPVerbFilter                     | Called for every SMTP command processed

| TLSHandler                         | Callback mashup called after STARTTLS

| GetAuthenticationMechanismsHandler | Called for each EHLO command



### Behaviour flags



The state machine also exports variables to control its behaviour:



See [![GoDoc](https://godoc.org/github.com/mailhog/smtp?status.svg)](https://godoc.org/github.com/mailhog/smtp) for more information.



| Variable               | Description

| ---------------------- | -----------

| RejectBrokenRCPTSyntax | Reject non-conforming RCPT syntax

| RejectBrokenMAILSyntax | Reject non-conforming MAIL syntax

| RequireTLS             | Require STARTTLS before other commands

| MaximumRecipients      | Maximum recipients per message

| MaximumLineLength      | Maximum length of SMTP line



### Licence



Copyright ©‎ 2014-2015, Ian Kent (http://iankent.uk)



Released under MIT license, see [LICENSE](LICENSE.md) for details.