SMTP Worker

Send queued e-mail in separate process through
a JSON abstraction.

Use of this source code is governed by a BSD-style
license that can be found in the LICENSE file.

Why?

Security, SMTP credentials are isolated from the website
Simplicity, the website creates JSON and all SMTP logic is isolated here
Scalable, things need to go faster? Start a second..third..fourth.. worker!
Cleaner, no more ugly timeouts in the browser if trouble and no more lost emails/customers!

How?

Use Beanstalkd (http://kr.github.io/beanstalkd/) to add jobs in a queue.
One or more SMTPw-instances read the queue and try to send
Failure? Wait 5sec on SMTPw error or wait for Beanstalk deadline (if process got killed) and try again!

Config

{
    "beanstalk": "127.0.0.1:11300",           // Hostname:port to Beanstalkd
    "from": {
        "support": {                            // From in JSON matches to this from
            "user": "emailuser",                  // SMTP username
            "pass": "supersecretpass",            // SMTP password
            "host": "smtp.yourcompany.com",       // SMTP hostname
            "port": 1234,                         // SMTP port
            "from": "support@yourcompany.com",    // From-address (used in mail header)
            "display": "RootDev",                 // Display-name added before From-address
            "bcc": [
                "alwayssendhere@yourcompany.com"    // Send a secret copy (can be useful for monitoring/debugging)
            ],
            "allowBCC": false                     // true to allow the BCC-field to be appended by the Email-struct
        }
    }
}

Be careful with Insecure=true as it will allow MITM (Man In The Middle Attacks)

Bounce sets the From-header to the bounce-address and
sets Reply-To for human replies.

Usage

./smtpw -h
Usage of ./smtpw:
  -c="./config.json": Path to config.json
  -s=false: Delete e-mail on deverr
  -v=false: Verbose-mode

Path config.json, where to find the config.json file
Delete on deverr, delete and flush the e-mail content if
JSON is invalid.
Verbose-mode, log what we’re doing

JSON

type Email struct {
    From        string          // Key that MUST match From in config
    To          []string
    BCC         []string        // Only used when allowBCC=true in config
    Subject     string
    Html        string
    Text        string
    HtmlEmbed   map[string]string // file.png => base64(bytes)
    Attachments map[string]string // file.png => base64(bytes)
}

WARN: I like my parsers strict. Every HtmlEmbed key is scanned with
Html.contains(cid:key) and if not found it will throw an error.

WARN: Invalid supplied email-address will fail with errors like
mail: no angle-addr, please use a descent email RFC validator, i.e. for PHP https://github.com/iamcal/rfc822

Errors

panic: dial tcp 127.0.0.1 connection refused
Install Beanstalkd and update config if Beanstalkd is running elsewhere?

x509: certificate signed by unknown authority
Your SMTP-server has a self-signed certificate? Time to get
a signed one!

Job never received by SMTPw?
Is the job sent to the email tube? As smtpw only listenes to this tube.

telnet 127.0.0.1 11300
use email
peek-ready << should show your JSON here

Systemd

# User + systemd
useradd -r smtpw
mkdir -p /home/smtpw
vi /etc/systemd/system/smtpw@.service
vi /etc/systemd/system/smtpw.target
chmod 644 /etc/systemd/system/smtpw@.service
chmod 644 /etc/systemd/system/smtpw.target
systemctl daemon-reload
systemctl enable smtpw@1
systemctl enable smtpw@2
systemctl start smtpw@1
systemctl start smtpw@2